RD Sharma Solutions Class 6 Maths Knowing Our Numbers - Exercise 1.8 PDF

Q1: Write the expression for each of the following statements using brackets:
(i) Four multiplied by the sum of 13 and 7.
(ii) Eight multiplied by the difference of four from nine.
(iii) Divide the difference of twenty eight and seven by 3.
(iv) The sum of 3 and 7 is multiplied by the difference of twelve and eight.
Ans:
(i) The expression for Four multiplied by the sum of 13 and 7 is 4 × (13 + 7).
Brackets show that 13 + 7 must be added first.
(ii) Eight multiplied by the difference of four from nine is 8 × (9 - 4).
Brackets indicate that 9 - 4 is found before multiplying by 8.
(iii) Divide the difference of twenty eight and seven by 3 is (28 - 7) ÷ 3.
Here the difference 28 - 7 is calculated first, then the result is divided by 3.
(iv) The sum of 3 and 7 is multiplied by the difference of twelve and eight is (3 + 7) × (12 - 8).
Both sums and differences inside brackets are evaluated before the multiplication.

Q2: Simplify each of the following:

(i) 124 - (12 - 2) × 9

(ii) (13 + 7) × (9 - 4) - 18

(iii) 210 - (14 - 4) × (18 + 2) - 10

Ans:
(i) 124 - (12 - 2) × 9
124 - (12 - 2) × 9
= 124 - 10 × 9
= 124 - 90
= 34
(ii) (13 + 7) × (9 - 4) - 18
(13 + 7) × (9 - 4) - 18
= 20 × 5 - 18
= 100 - 18
= 82
(iii) 210 - (14 - 4) × (18 + 2) - 10
210 - (14 - 4) × (18 + 2) - 10
= 210 - 10 × 20 - 10
= 210 - 200 - 10
= 0