Page 76 - Maths Skills - 7

74 Maths

8 3 8 7 8 1 8 − 8 2 − 8 7 − 4 1 − 4
Solution: (i) ÷ = × = × = (ii) ÷ = × = ×=
21 7 21 3 3 3 9 35 7 35 2 5 1 5

20 − 5 20 3 20 3× 41× 4
(iii) ÷ = × = = =
21 3 21 − 5 21×−( 5) 7 ×−( 1) − 7

− 44 −11
Example 3: By what number should be divided to get ?
3 12
Solution: Let the required number be x then
− 44 ÷ x = −11 ⇒ − 44 × 1 = −11

3 12 3 x 12

1 −11  −44  −11 3 1 1
⇒ = ÷   = × ⇒ = ⇒ x = 16
x 12  3  12 44 x 16
4 4

Exercise 4.6

1. Simplify.
− 64 72 1 11 −12
(i) ÷ (ii) 3 ÷ (iii) ÷−18( )
42 28 7 12 7
− 
3  5 4  − 7 
9
(iv) (− 6 ) ÷ 3 (v) −÷   (vi) ÷  
5  18  15  21 
2. Evaluate the following.

(i)  3 × 5   9 ÷ 3  (ii)  3 4 ÷ 5  × 1 1
−



 

 11 6   22 4   7 49  4
3. The product of two rational numbers is – 11. If one of the numbers is – 12, find the other.
32 9
4. Divide the sum of and and by their difference.
15 11
5. By what number should we multiply –15 , so that the product is –5
28 7 ?

6. By what rational number should –12 be multiplied to obtain 39?
52
1 1
7. The cost of 4 metres of cloth is ` 85 . Find the cost of one metre cloth.
2 2

8. Find the value of
−   4
 7 −1 3  7 − 
− 
÷
(i) −÷   (ii) ÷ (iii)    
6
 5  9 4  12   6 
7 14 19 21 9
(iv) ÷ (v) −÷1 (vi) ÷
17 51 9 9 21