NCERT Solutions Class 6 Mathematics Chapter 11 Algebra

Exercise: 11.1

Q.1) Find the rule which gives the number of matchsticks required to make the following matchstick patterns. Use a variable to write the rule.

Sol.1) a) Let us write the letter n for the number of T’s.
If one T is made, 𝑛 = 1; if two T’s are made, 𝑛 = 2 and so on; 
thus, n can be any natural number 1, 2, 3, 4, 5 …
We see that 2 matchsticks are required for making one letter T. So,
For 𝑛 = 1, the number of matchsticks required is 2 × 1 = 2. [T]
For 𝑛 = 2, the number of matchsticks required is 2 × 2 = 4. [TT]
For 𝑛 = 3, the number of matchsticks required is 2 × 3 = 6. [TTT] …
For 𝑛 number of T’s, the number of matchsticks requires is = 2 × 𝑛 = 2𝑛

b) Let us write the letter n for the number of Z’s.
If one Z is made, 𝑛 = 1; if two Z’s are made, 𝑛 = 2 and so on;
thus, 𝑛 can be any natural number 1, 2, 3, 4, 5 …
We see that 3 matchsticks are required for making one letter Z. So,
For 𝑛 = 1, the number of matchsticks required is 3 × 1 = 3. [Z]
For 𝑛 = 2, the number of matchsticks required is 3 × 2 = 6. [ZZ]
For 𝑛 = 3, the number of matchsticks required is 3 × 3 = 9. [ZZZ]…
For 𝑛 number of Z’s, the number of matchsticks requires is = 3 × 𝑛 = 3𝑛

c) Let us write the letter n for the number of U’s.
If one U is made, 𝑛 = 1; if two U’s are made, 𝑛 = 2 and so on;
thus, 𝑛 can be any natural number 1, 2, 3, 4, 5 …
We see that 3 matchsticks are required for making one letter U. So,
For 𝑛 = 1, the number of matchsticks required is 3 × 1 = 3. [U]
For 𝑛 = 2, the number of matchsticks required is 3 × 2 = 6. [UU]
For 𝑛 = 3, the number of matchsticks required is 3 × 3 = 9. [UUU]…
For 𝑛 number of U’s, the number of matchsticks requires is = 3 × 𝑛 = 3𝑛

d) Let us write the letter 𝑛 for the number of V’s.
If one V is made, 𝑛 = 1; if two V’s are made, 𝑛 = 2 and so on;
thus, 𝑛 can be any natural number 1, 2, 3, 4, 5 …
We see that 2 matchsticks are required for making one letter V. So,
For 𝑛 = 1, the number of matchsticks required is 2 × 1 = 2. [V]
For 𝑛 = 2, the number of matchsticks required is 2 × 2 = 4. [VV]
For 𝑛 = 3, the number of matchsticks required is 2 × 3 = 6. [VVV] …
For 𝑛 number of V’s, the number of matchsticks requires is = 2 × 𝑛 = 2𝑛

e) Let us write the letter n for the number of E’s.
If one E is made, 𝑛 = 1; if two E’s are made, 𝑛 = 2 and so on;
thus, 𝑛 can be any natural number 1, 2, 3, 4, 5 …
We see that 5 matchsticks are required for making one letter E. So,
For 𝑛 = 1, the number of matchsticks required is 5 × 1 = 5. [E]
For 𝑛 = 2, the number of matchsticks required is 5 × 2 = 10. [EE]
For 𝑛 = 3, the number of matchsticks required is 5 × 3 = 15. [EEE] …
For 𝑛 number of E’s, the number of matchsticks requires is = 5 × 𝑛 = 5𝑛

f) Let us write the letter 𝑛 for the number of S’s.
If one S is made, 𝑛 = 1; if two S’s are made, 𝑛 = 2 and so on;
thus, 𝑛 can be any natural number 1, 2, 3, 4, 5 …
We see that 5 matchsticks are required for making one letter S. So,
For 𝑛 = 1, the number of matchsticks required is 5 × 1 = 5. [S]
For 𝑛 = 2, the number of matchsticks required is 5 × 2 = 10. [SS]
For 𝑛 = 3, the number of matchsticks required is 5 × 3 = 15. [SSS] …
For n number of S’s, the number of matchsticks requires is = 5 × 𝑛 = 5𝑛

g) Let us write the letter n for the number of A’s.
If one A is made, 𝑛 = 1; if two A’s are made, 𝑛 = 2 and so on;
thus, 𝑛 can be any natural number 1, 2, 3, 4, 5 …
We see that 6 matchsticks are required for making one letter A. So,
For 𝑛 = 1, the number of matchsticks required is 6 × 1 = 6. [A]
For 𝑛 = 2, the number of matchsticks required is 6 × 2 = 12. [AA]
For 𝑛 = 3, the number of matchsticks required is 6 × 3 = 18. [AAA] …
For 𝑛 number of A’s, the number of matchsticks requires is = 6 × 𝑛 = 6𝑛

Q.2) We already know the rule for the pattern of letters L, C and F. Some of the letters from Q.1 (given above) give us the same rule as that given by L. Which are these? Why does this happen?
Sol.2) (a) And (d), that is, letters T and V have the same pattern rule as for letters L, C and F as the number of matchsticks required to make the letter is 2.

Q.3) Cadets are marching in a parade. There are 5 cadets in a row. What is the rule which gives? The number of cadets, given the number of rows? (Use 𝑛 for the number of rows.)
Sol.3) Number of rows = 𝑛

𝑛 is a variable that can take any value 1, 2, 3, 4, …
Number of cadets in a row = 5
Total number of cadets is given by the rule = 5 × number of rows
                                                              = 5𝑛
Q.4) If there are 50 mangoes in a box, how will you write the total number of mangoes in terms of the number of boxes? (Use b for the number of boxes.)
Sol.4) Number of boxes is given by the variable 𝑏.
Number of mangoes in one box = 50
So, total number of mangoes is given by the rule = 50 × number of boxes
                                                                       = 50𝑏

Q.5) The teacher distributes 5 pencils per student. Can you tell how many pencils are needed given the number of students? (Use 𝑠 for the number of students.)
Sol.5) Number of students is given by the variable 𝑠.
Number of pencils given to one student = 5
So, total number of pencils is given by the rule = 5 × number of students
                                                                    = 5𝑠

Q.6) A bird flies 1 kilometre in one minute. Can you express the distance covered by the bird in, terms of its flying time in minutes? (Use 𝑡 for flying time in minutes.)
Sol.6) Flying time in minutes is given by the variable 𝑡.
Distance fled by the bird in one minute is 1 𝑘𝑚
Distance covered by the bird in minutes is given by the rule = distance covered in 1 min × flying time = 1 × 𝑡 = 𝑡 𝑘𝑚.

Q.7) Radha is drawing a dot Rangoli (a beautiful pattern of lines joining dots) with chalk powder. She has 9 dots in a row. How many dots will her Rangoli have for r rows? How many dots are there if there are 8 rows? If there are 10 rows?
Sol.7) Number of dots in a row = 9
Number of rows is a variable 𝑟.
Total number of dots in r rows = number of dots in one row × number of rows
                                            = 9𝑟
Total number of dots in 8 rows = number of dots in one row × number of rows
                                             = 9 × 8 = 72
Total number of dots in 10 rows = number of dots in one row × number of rows
                                               = 9 × 10 = 90

Q.8) Leela is Radha's younger sister. Leela is 4 years younger than Radha. Can you write Leela's age in terms of Radha's age? Take Radha's age to be 𝑥 years.
Sol.8) Radha's age = 𝑥 𝑦𝑒𝑎𝑟𝑠
Leela is 4 years younger than Radha, i.e. Radha’s age – 4
Leela’s age = 𝑥 – 4 𝑦𝑒𝑎𝑟𝑠

Q.9) Mother has made laddus. She gives some laddus to guests and family members; still 5 laddus remain. If the number of laddus mother gave away is l, how many laddus did she make?
Sol.9) Number of laddus mother gave away = 𝑙.
Number of laddus remaining = 5
Total number of laddus she made = 𝑙 + 5

Q.10) Oranges are to be transferred from larger boxes into smaller boxes. When a large box is emptied, the oranges from it fill two smaller boxes and still 10 oranges remain outside. If the number of oranges in a small box are taken to be 𝑥, what is the number of oranges in the larger box?
Sol.10) Number of oranges in the small box = 𝑥
When a large box is emptied, the oranges from it fill two smaller boxes and still 10 oranges remain outside.
That is, Number of oranges in the larger box = Number of oranges in two small boxes +
10 oranges = 𝑥 + 𝑥 + 10
= 2𝑥 + 10

Q.11) (a) Look at the following matchstick pattern of squares (Fig 11.6). The squares are not separate. Two neighbouring squares have a common matchstick. Observe the patterns and find the rule that gives the number of matchsticks in terms of the number of squares.

So the pattern for n number of triangles is 1 more than twice the number of triangles, 𝑛, OR 2𝑛 + 1

Exercise: 11.2

Q.1) The side of an equilateral triangle is shown by 𝑙. express the perimeter of the equilateral triangle using 𝑙.
Sol.1) An equilateral triangle has three equal sides, 𝑙 and its perimeter is the sum of the three sides,
Length of side of equilateral triangle = 𝑙
Perimeter of equilateral triangle = 𝑙 + 𝑙 + 𝑙 = 3𝑙 .

Q.2) The side of a regular hexagon (fig: 11.10) is denoted by 𝑙. Express the perimeter of the hexagon using 𝑙.

Sol.2) Given, the each side of a regular hexagon = 𝑙
Perimeter of the regular hexagon = sum of all sides
= 𝑙 + 𝑙 + 𝑙 + 𝑙 + 𝑙 + 𝑙 = 6𝑙

Q.3) A cube is a three-dimensional figure as shown in fig: 11.11. It has six faces and all of them are identical squares. The length of an edge of the cube is given by l. Find the formula for the total length of the edges of a cube.
Sol.3) Length of one edge of a cube = 𝑙
Total number of edges in a cube = 12
Total length of the edges of a cube = No. of edges × length of one edge
= 12 × 𝑙 = 12𝑙
So, Total length of the edges of a cube is 12 𝑙 .

Q.4) The diameter of a circle is a line which joins two points on the circle and also passes through the centre of the circle. (In the adjoining fig: 11.12) 𝐴𝐵 is a diameter of the circle; 𝐶 is its centre. Express the diameter of the circle (𝑑) in terms of its radius (𝑟).
Sol.4) 𝐶 is the centre of the circle.
𝐴𝐶 and 𝐶𝐵 are the radius(𝑟) of the circle.
Diameter of a circle is double of radius.
So, Diameter 𝐴𝐵 = 𝐴𝐶 + 𝐶𝐵 = 𝑟 + 𝑟 = 2𝑟

Q.5) To find sum of three numbers 14, 27 and 13, we can have two ways:
(a) We may first add 14 and 27 to get 41 and then add 13 to it to get the total sum 54 or
(b) We may add 27 and 13 to get 40 and then add 14 to get the sum 54.
Thus, (14 + 27) + 13 = 14 + (27 + 13)
This can be done for any three numbers. This property is known as the associativity of addition of numbers. Express this property which we have already studied in the chapter on Whole Numbers, in a general way, by using variables 𝑎, 𝑏 and 𝑐.
Sol.5) For any three whole numbers a, b, and c
(𝑎 + 𝑏) + 𝑐 = 𝑎 + (𝑏 + 𝑐)

Exercise: 11.3

Q.1) Make up as many expressions with numbers (no variables) as you can from three numbers 5, 7 and 8. Every number should be used not more than once. Use only addition, subtraction and multiplication.
Sol.1) Some expressions that can be formed using 5, 8 and 7 are given below.
5 – (8 + 7), 5 + (8 + 7), 5 × (8 + 7), 5 – (8 × 7), 5 + (8 × 7), 5 – (8 – 7) …
[Many such expressions can be formed using the numbers]

Q.2) Which out of the following are expressions with numbers only?
(a) 𝑦 + 3 (b) (7 × 20) – 8𝑧 (c) 5(21 – 7) + 7 × 2 (𝑑) 5
(e) 3𝑥 (f) 5 – 5𝑛 (g) (7 × 20) − (5 × 10) − 45 + 𝑝
Sol.2) Expression (c) and (d) are expressions with only numbers.

Q.3) Identify the operations (addition, subtraction, division, multiplication) in forming the following expressions and tell how the expressions have been formed.
(a) 𝑧 + 1, 𝑧 – 1, 𝑦 + 17, 𝑦 – 17
(b) 17𝑦, 𝑦/17, 5 𝑧
(c) 2𝑦 + 17, 2 𝑦 – 17
(d) 7 𝑚, – 7 𝑚 + 3, – 7 𝑚 – 3
Sol.3) a) 1 is added to 𝑧, 1 is subtracted from 𝑧, 17 is added to y and 17 is subtracted from y.
So, operations involved are addition, subtraction, addition, subtraction.
b) 17 and 𝑦 are multiplied, 𝑦 is divided by 17, 5 is multiplied to 𝑧. So, the operations involved are multiplication, division and multiplication.
c) 𝑦 is multiplied by 2 and is added to 17, 𝑦 is multiplied by 2 and 17 is subtracted from the product. So the operations involved are multiplication and addition, multiplication and subtraction.
d) 𝑚 is multiplied to 7, 𝑚 is multiplied to -7 and 3 added, 𝑚 is multiplied to -7 and 3 subtracted. So, the operations involved are multiplication, multiplication and addition, multiplication and subtraction.

Q.4) Give expressions for the following cases.
(a) 7 added to 𝑝 (b) 7 subtracted from 𝑝
(c) 𝑝 multiplied by 7 (d) 𝑝 divided by 7
(e) 7 subtracted from – 𝑚 (f) – 𝑝 multiplied by 5
(g) – 𝑝 divided by 5 (h) 𝑝 multiplied by – 5
Sol.4) (a) 7 + 𝑝        b) 𝑝 – 7
c) 7 𝑝                       d) 𝑝/7
e) – 𝑚 – 7                f) −5𝑝
g) – (𝑝/5)                 h) −5𝑝

Q.5) Give expressions in the following cases.
(a) 11 added to 2𝑚
(b) 11 subtracted from 2𝑚
(c) 5 times 𝑦 to which 3 is added
(d) 5 times 𝑦 from which 3 is subtracted
(e) 𝑦 is multiplied by – 8
(f) 𝑦 is multiplied by – 8 and then 5 is added to the result
(g) 𝑦 is multiplied by 5 and the result is subtracted from 16
(h) 𝑦 is multiplied by – 5 and the result is added to 16.
Sol.5) a) 11 + 2𝑚
b) 2𝑚 – 11
c) 5𝑦 + 3
d) 5𝑦 – 3
e) −8𝑦
f) −8𝑦 + 5
g) 16 – 5𝑦
h) −5𝑦 + 16

Q.6) (a) Form expressions using 𝑡 and 4. Use not more than one number operation. Every expression must have 𝑡 in it.
(b) Form expressions using 𝑦, 2 and 7. Every expression must have 𝑦 in it. Use only two number operations. These should be different.
Sol.6) a) 𝑡 + 4, 𝑡 – 4, 4𝑡, 𝑡/4, 4/𝑡, 4 – 𝑡
b) 2𝑦 + 7, 2𝑦 – 7, 2𝑦/7, 7/2𝑦 , 2 + 7𝑦 …
[Many expressions can be formed]

Exercise: 11.4

Q.1) a) Take Sarita’s present age to be y years
(i) What will be her age 5 years from now?
(ii) What was her age 3 years back?
(iii) Sarita’s grandfather is 6 times her age. What is the age of her grandfather?
(iv) Grandmother is 2 years younger than grandfather. What is grandmother's age?
(v) Sarita’s father’s age is 5 years more than 3 times Sarita’s age. What is her father's age?
(b) The length of a rectangular hall is 4 meters less than 3 times the breadth of the hall.
What is the length, if the breadth is b meters?
(c) A rectangular box has height h cm. Its length is 5 times the height and breadth is 10 cm less than the length. Express the length and the breadth of the box in terms of the height.
(d) Meena, Beena and Leena are climbing the steps to the hill top. Meena is at step s, Beena is 8 steps ahead and Leena 7 steps behind. Where are Beena and Meena? The total number of steps to the hill top is 10 less than 4 times what Meena has reached. Express the total number of steps using 𝑠.
(e) A bus travels at v km per hour. It is going from Daspur to Beespur. After the bus has travelled 5 hours, Beespur is still 20 km away. What is the distance from Daspur to Beespur? Express it using 𝑣.
Sol.1) a)
i) Sarita’s present age is y years.
Her age 5 years from now will be her present age + 5 = 𝑦 + 5 𝑦𝑒𝑎𝑟𝑠.
ii) Her age 3 years back will be her present age – 3 𝑦𝑒𝑎𝑟𝑠 = 𝑦 – 3 𝑦𝑒𝑎𝑟𝑠
iii) Sarita’s grandfather is 6 times her age = 6𝑦 𝑦𝑒𝑎𝑟𝑠
iv) Grandmother’s age = Grandfather’s age – 2 = 6𝑦 – 2 𝑦𝑒𝑎𝑟𝑠
v) Sarita’s father’s age is 5 years more than 3 times Sarita’s age = 5 + 3𝑦
b) breadth of the rectangular hall = 𝑏 𝑚𝑒𝑡𝑒𝑟𝑠
length of the hall = 4 meters less than 3 times the breadth = 3𝑏 – 4 𝑚𝑒𝑡𝑒𝑟𝑠
c) height of the rectangular box = ℎ 𝑐𝑚
length = 5 𝑡𝑖𝑚𝑒𝑠 the height = 5ℎ 𝑐𝑚
breadth = 10 𝑐𝑚 less than the length = 5ℎ – 10 𝑐𝑚
d) Step at which Meena is 𝑠
Step at which Beena is = Meena’s step + 8 𝑠𝑡𝑒𝑝𝑠 = 𝑠 + 8
Step at which Leena is = Meena’s step – 7 = 𝑠 – 7
Total number of steps = 4𝑠 – 10
e) Distance travelled by the bus in 1 ℎ𝑜𝑢𝑟 = 𝑣 𝑘𝑚
Distance travelled in 5 ℎ𝑜𝑢𝑟𝑠 = 5𝑣 𝑘𝑚
So, total distance from Daspur to Beespur = Distance travelled in 5 hours + 20 = 5𝑣 + 20 𝑘𝑚

Q.2) Change the following statements using expressions into statements in ordinary 𝑠 language.
(For example, Given Salim scores 𝑟 runs in a cricket match, Nalin scores (r + 15) runs. In ordinary language – Nalin scores 15 runs more than Salim.)
(a) A notebook costs 𝑅𝑠 𝑝. A book costs 𝑅𝑠 3 𝑝.
(b) Tony puts 𝑞 marbles on the table. He has 8 𝑞 marbles in his box.
(c) Our class has 𝑛 students. The school has 20 𝑛 students.
(d) Jaggu is 𝑧 years old. His uncle is 4 𝑧 𝑦𝑒𝑎𝑟𝑠 old and his aunt is (4𝑧 – 3) 𝑦𝑒𝑎𝑟𝑠 𝑜𝑙𝑑.
(e) In an arrangement of dots there are 𝑟 rows. Each row contains 5 𝑑𝑜𝑡𝑠.
Sol.2) a) The cost of a book is three times the cost of a notebook.
b) Tony has 8 times the number of marbles in his box than on the table.
c) Total number of students in the class is 20 times that of our class.
d) Jaggu’s uncle is 4 times the age of Jaggu and his aunt is 3 less than 4 times the age of Jaggu.
e) The total number of dots is 5 times the number of rows.

Q.3) (a) Given Munnu’s age to be 𝑥 years, can you guess what (𝑥 – 2) may show?
Can you guess what (𝑥 + 4) may show? What (3 𝑥 + 7) may show?
(b) Given Sara’s age today to be 𝑦 years. Think of her age in the future or in the past.
What will the following expression indicate?
𝑦 + 7, 𝑦 – 3, 𝑦 + 4 (1/2), 𝑦 – 2 (1/2)
(c) Given n students in the class like football, what may 2𝑛 show? What may 𝑛/2 show?
Sol.3) a) If Munnu’s age is 𝑥 years, then (𝑥 – 2) may show the age is 2 years younger than Munnu.
(𝑥 + 4) shows that the age is 4 years older than Munnu and 3𝑥 + 7 shows that the age considered is 7 more than thrice the age of Munnu.
b) Sara’s present age = 𝑦 𝑦𝑒𝑎𝑟𝑠
𝑦 + 7 represents her future age, i.e., her age after 7 years.
𝑦 – 3 represents her past age, i.e. her age 3 years ago.
𝑦 + 4(1/2) represents her future age, i.e her age after 4(1/2) years
𝑦 – 2(1/2) represents her past age, i.e. her age 2(1/2) years ago.
c) 2n represents twice the number of students who like football.
𝑛/2 represents half the number of students who like football.
It may represent the number of students who like cricket, or basketball etc.

Exercise 11.5

Q.1) State which of the following are equations (with a variable). Give reason for your answer.
Identify the variable from the equations with a variable.
a) 17 = 𝑥 + 7                b) (𝑡 − 7) > 5                       c) 4/2 = 2
d) (7 × 3) − 19 = 8       e) 5 × 4 − 8 = 2𝑥                  f) (7 × 3) − 19 = 8
g) 2𝑚 < 30                  h) 2𝑛 + 1 = 11                      i) 7 = (11 × 5) − (12 × 4)
j) 7 = (11 × 2) + 𝑝        k) 20 + 5𝑦                             l) 3𝑞/2 < 5
m) 𝑧 + 12 > 24            n) 20 − (10 − 5) = 3 × 5       o) 7 − 𝑥 = 5
Sol.1) a) Is an equation with one variable, 𝑥.
b) Is not an equation, is an in equation.
c) Is not an equation, it is a numerical equation.
d) Is not an equation, it is a numerical equation.
e) Is not an equation, is an in equation.
f) Is an equation with one variable, 𝑥.
g) Is not an equation, is an in equation.
h) Is an equation with one variable, 𝑛.
i) Is not an equation, it is a numerical equation.
j) Is an equation with one variable, 𝑝.
k) Is an equation with one variable, 𝑦.
l) Is not an equation, is an in equation
m) Is not an equation, is an in equation.
n) Is not an equation, it is a numerical equation.
o) Is an equation with one variable, 𝑥.

Q.2) Complete the entries in the third column of the table.
S.No.      Equation         Value of variable        Equation satisfied Yes/No
(a)          10y = 80             y = 10
(b)          10y = 80             y = 8
(c)          10y = 80             y = 5
(d)            4l = 20              l = 20
(e)            4l = 20              l = 80
(f)             4l = 20              l = 5
(g)             b + 5 = 9          b = 5
(h)             b + 5 = 9          b = 9
(i)              b + 5 = 9          b = 4
(j)              h – 8 = 5           h = 13
(k)             h – 8 = 5           h = 8
(l)              h – 8 = 5           h = 0
(m)            p + 3 = 1           p = 3
(n)             p + 3 = 1           p = 1
(o)             p + 3 = 1           p = 0
(p)             p + 3 = 1           p = – 1
(q)             p + 3 = 1           p = – 2
Sol.2)

Q.3) Pick out the solution from the values given in the bracket next to each equation.
Show that the other values do not satisfy the equation.
(a) 5m = 60              (10, 5, 12, 15)
(b) n + 12 = 20        (12, 8, 20, 0)
(c) p − 5 = 5             (0, 10, 5 − 5)
(d) 𝑞/2 = 7               (7, 2, 10, 14)
(e) r − 4 = 0             (4, − 4, 8, 0)
(f) x + 4 = 2             (− 2, 0, 2, 4)
Sol. 3) a) 5𝑚 = 60
For 𝑚 = 10, 5𝑚 = 5(10) = 50
For 𝑚 = 5, 5𝑚 = 5(5) = 25
For 𝑚 = 12, 5𝑚 = 5(12) = 60
For 𝑚 = 15, 5𝑚 = 5(15) = 75
So, we see that 𝑚 = 12 satisfy the equation and is the solution.

b) 𝑛 + 12 = 20
For 𝑛 = 12, 𝑛 + 12 = 12 + 12 = 24
For 𝑛 = 8, 𝑛 + 12 = 8 + 12 = 20
For 𝑛 = 20, 𝑛 + 12 = 20 + 12 = 32
For 𝑛 = 0, 𝑛 + 12 = 0 + 12 = 12
So, we see that 𝑛 = 8 satisfy the equation and is the solution.

c) 𝑝 – 5 = 5
Let's try the equation of each given value of 𝑝
For 𝑝 = 0, 𝑝 – 5 = 0 – 5 = −5
For 𝑝 = 10, 𝑝 – 5 = 10 – 5 = 5
For 𝑝 = 5, 𝑝 – 5 = 5 – 5 = 0
For 𝑝 = −5, 𝑝 – 5 = −5 – 5 = −10
So, we see that 𝑝 = 10 satisfy the equation and is the solution.

d) 𝑞/2 = 7
For 𝑞 = 7, 𝑞/2 = 7/2
For 𝑞 = 2, 𝑞/2 = 2/2 = 1
For 𝑞 = 10, 𝑞/2 = 10/2 = 5
For 𝑞 = 14, 𝑞/2 = 14/2 = 7
So, we see that 𝑞 = 14 satisfy the equation and is the solution.

e) 𝑟 – 4 = 0
For 𝑟 = 4, 𝑟 – 4 = 4 – 4 = 0
For 𝑟 = −4, 𝑟 – 4 = −4 – 4 = −8
For 𝑟 = 8, 𝑟 – 4 = 8 – 4 = 4
For 𝑟 = 0, 𝑟 – 4 = 0 – 4 = −4
So, we see that 𝑟 = 4 satisfy the equation and is the solution.

f) 𝑥 + 4 = 2
For 𝑥 = −2, 𝑥 + 4 = −2 + 4 = 2
For 𝑥 = 0, 𝑥 + 4 = 0 + 4 = 4
For 𝑥 = 2, 𝑥 + 4 = 2 + 4 = 6
For 𝑥 = 4, 𝑥 + 4 = 4 + 4 = 8
So, we see that 𝑥 = −2 satisfy the equation and is the solution.

Q.4) (a) Complete the table and by inspection of the table, find the solution to the equation 𝑚 + 10 = 16.

From the table, solution for equation 𝑚 − 7 = 3 is 𝑚 = 10

Q.5) Solve the following riddles, you may yourself construct such riddles.
Who am I?
(i) Go round a square
Counting every corner
Thrice and no more!
Add the count to me
To get exactly thirty-four!
(ii) For each day of the week
Make an up count from me
If you make no mistake
You will get twenty-three!
(iii) I am a special number
Take away from me a six!
A whole cricket team
You will still be able to fix!
(iv) Tell me who I am
I shall give a pretty clue!
You will get me back
If you take me out of twenty two!
Sol.5) i)
A square has 4 sides.
“Counting every corner Thrice and no more!”
Implies we go around the square thrice, i.e. 12 𝑡𝑖𝑚𝑒𝑠.
“Add the count to me to get exactly thirty-four!”
That is, when 12 is added to a number
Let us assume the number as 𝑦, we get 34.
12 + y = 34
y = 34 – 12 = 22
So, 22 is the number.

ii) If 23 is the number for Sunday,
Then counting up,
Saturday is 22, Friday is 21, Thursday is 20, Wednesday is 19, Tuesday is 18, Monday is
17 and Sunday is 16.
Therefore, the number considered is 16.

iii) Let the number be 𝑥.
If we take away 6 from 𝑥, we get a cricket team. [A cricket team has 11 players].
𝑥 – 6 = 11
𝑥 = 11 + 6 = 17
The special number is 17.

iv) Let the number be 𝑥.
22 – 𝑥 = 𝑥
22 = 𝑥 + 𝑥 = 2𝑥
𝑥 = 22/2 = 11
The number is 11.

 

Question. The patterns below are made with circles. How many circles will be needed to make the TENTH figure if the patterns are continued?

(a) 10
(b) 12
(c) 19
(d) 70

Answer : C

Question. 10 matchsticks can be arranged to form rectangles in exactly 2 DIFFERENT ways. Look at the figures below : (No matchstick can be bent or broken)Similarly, in how many different ways can 14 matchsticks be arranged to form rectangles?

(a) 2
(b) 3
(c) 4
(d) 7

Answer : B

Question. Triangular numbers are the numbers formed by counting the number of objects used to form triangular arrangements as shown below. What is the triangular number corresponding to a triangle with a base of 10 objects?

(a) 10
(b) 25
(c) 50
(d) 55

Answer : D

Question. When two numbers are multiplied, the result is 864. If both the original numbers were doubled and then multiplied, what would the result have been?
(a) 864
(b) 868
(c) 1728
(d) 3456

Answer : D

Question. (5 + 5) + (5 + 6) + (5 + 7) + (5 + 8) + .... + (5 + 14) + (5 + 15) = (11 times 10) + what number?
(a) 15
(b) 50
(c) 55
(d) 99

Answer : C

Question. Which letter will be at the centre of the bottom row of the next triangle in the pattern?

(a) d
(b) e
(c) f
(d) g

Answer : C

Question. How many letters will there be in the bottom row of the fifth triangle in the pattern?

(a) 5
(b) 9
(c) 11
(d) 25

Answer : C

Question. There are 10 balls in a bag, which are yellow, blue or red in colour. Out of these, 5 are NOT blue and 7 are NOT red. How many yellow balls are there in the bag?
(a) 2
(b) 3
(c) 5
(d) 8

Answer : A

Question. The difference between two numbers is 3452. If both the original numbers are halved and then subtracted, what can we say about the new difference?
(a) It will be 1726.
(b) It will be 3452.
(c) It will be 7904.
(d) It will depend on the numbers. 

Answer : A

Question. If you divide the number of teeth that this monster has by 3 and then subtract 1 from it, you get the number of arms it has. How many teeth does the monster have? 

(a) 21
(b) 18
(c) 15
(d) 10

Answer : A

Question. Tapan thinks of a number, doubles it and adds 50 to the answer. He gets the answer 120. What was Tapan's original number?
(a) 290
(b) 70
(c) 35
(d) 20

Answer : C

Question. Ramdin has a buffalo, a dog and a donkey. The donkey's weight is 0. 25 times that of the buffalo. The dog weighs 20 kg less than the donkey. If the buffalo weighs 240 kg, the dog's weight is
(a) 280 Kg
(b) 60 Kg
(c) 40 Kg
(d) 30 Kg

Answer : C

Question. Two units of measuring temperature are Celsius ( ᵒ C ) and Fahrenheit ( ᵒ F).  If we multiply a Celsius temperature by 9, then divide it by 5 and then add 32, we get the Fahrenheit temperature. How much is 15 ᵒ C in Fahrenheit?
(a) 41 ^ᵒF
(b) 59 ^ᵒF
(c) 85 ^ᵒF
(d) 100 ^ᵒF

Answer : B

Question. Salma designs a tiled pathway having a single row of tiles. The tiles are of four colours: RED, GREEN, WHITE and BLACK, and the arrangement is as follows:1 Red tile - 2 Green tiles - 3 White tiles - 4 Black tiles, then 5 Red tiles - 6 Green tiles, and so on. What will be the colour of the 50th tile?
R G G W W W B B B B R R •••••••
(a) Red
(b) Green
(c) White
(d) Black

Answer : B

Question. An object X is weighed as shown below:
Which of the following weighing is POSSIBLE with the same object?

Answer : C