Page 68 - Maths Skill - 3

66 Maths

� For multiplying a number by 20, 30, 40, 50, ..., 90, we multiply the number by 2, 3,
4, 5, ..., 9 respectively and put a zero to the right of the product.

For example, 6 × 40 = (6 × 4) × 10 = 24 × 10 = 240

Multiply by Hundreds

� To multiply a number by 100, we multiply the number by 1 and put two zeros to
the right of the product.

For example, 7 × 100 = 700; 9 × 100 = 900

� For multiplying a number by 200, 300, 400 ..., 900, we multiply the number by 2, 3,
4, ... , 9 and put two zeros to the right of the product.

For example, 6 × 200 = (6 × 2) × 100 = 12 × 100 = 1200

Multiply by Thousands

� To multiply a number by 1000, we multiply the number by 1 and put three zeros
to the right of the product.

For example, 8 × 1000 = 8000; 7 × 1000 = 7000

� For multiplying a number by 2000, Fact-o-meter
3000, 4000 ..., 9000, we multiply the
number by 2, 3, 4, ... , 9 and put three To multiply a number by 9, first multiply
the number by 10 and then subtract the
zeros to the right of the product. number from the product.

For example, 3 × 3000 = (3 × 3) × 1000 For example, 23 × 9 = 23 × 10 – 23

= 9 × 1000 = 9000 = 230 – 23 = 207

Exercise 5.5

1. Write the product in the boxes.

(a) 9 × 10 = (b) 15 × 10 = (c) 35 × 10 =

(d) 8 × 40 = (e) 7 × 70 = (f) 9 × 80 =

2. Write the product in the boxes.

(a) 6 × 100 = (b) 15 × 100 = (c) 34 × 100 =

(d) 5 × 500 = (e) 9 × 100 = (f) 8 × 900 =

3. Multiply the following.

(a) 3 × 1000 = (b) 4 × 2000 = (c) 9 × 1000 =

(d) 1 × 3000 = (e) 2 × 3000 = (f) 2 × 2000 =