Page 75 - Maths Skills - 7

Rational Numbers 73

2. Multiply.

3 5 − 2 9 11 −36 121 –15 12
(i) by (ii) by (iii) by 36 (iv) by (v) by
4 7 3 7 6 11 12 4 –5
3. Simplify.

4 − 7 − 7 5 3 5 − 5 7 − 9 −16
(i) − 14 × 16 (ii) × (iii) × (vi) 21 × −15 (v) ×
30 14 20 4 8 3
4. Multiply.

− 60 7 3 55 19 − 51 90 − 35
(i) by (ii) by (iii) by (iv) by
21 20 11 − 60 17 33 155 126

7 19 145 134 1 9 52 57
(v) by (vi) by (vii) by (viii) by
− 19 7 − 67 29 − 3 − 27 19 13
2 3 12 –34
5. Multiply the sum of and by the sum of and .
5 4 17 4
–3 2 6 –26
6. Multiply the sum of and by the product of and .
7 3 13 9
1
1
7. Find the area of the rectangular garden with a length 7 m and a width of 4 m.
4
9
1
8. Jerry is building a scale model of a racing car. If the tyres on the actual car are 33 cm in radius, what
9
is the radius of the tyres in the model?
1
9. An equilateral triangle has a side of 3 cm. Find the perimeter of the triangle.
7
1
10. A box weighs 13 kg. Find the weight of 40 such boxes.
3

Division of Rational Numbers
p r r
In general, if and are any two rational numbers such that ≠ 0,
q s s
p r p r p s
then ÷ = × (reciprocal of ) is = ×
q s q s q r

Let’s learn through examples.

Let’s Attempt

− 24 − 8
Example 1: The product of two rational numbers is . If one of the numbers is , find the other number.
23 3
− 24 − 8 − 24  3  − 24 × − 3( ) 9
Solution: The other number is ÷ = ×−  = = .

23 3 23  8  23 × 8 23
Example 2: Divide.
8 3 − 8 2 20 − 5
(i) by (ii) by (iii) by
21 7 35 7 21 3