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Multiplying by 10, 20, 30, ..., 90, and 100, 200, 300, ..., 900

Multiplying by 10

To multiply a number by 10, write ‘0’ to the right of the number.

Look at the following multiplications.

Examples: (a) 3 × 10 = 30 (b) 12 × 10 = 120 (c) 324 × 10 = 3240
Multiplying by 20, 30,..., 90

To multiply a number by 20, 30, 40, ..., 90, first multiply the number without 0. Then,
write ‘0’ to the right of the product.

Examples: (a) 12 × 20 = 240 (b) 36 × 30 = 1080 (c) 26 × 60 = 1560
Multiplying by 100 12 × 2 36 × 3 26 × 6

To multiply a number by 100, write two zeros (00) to the right of the number.

Examples: (a) 1 × 100 = 100 (b) 5 × 100 = 500 (c) 12 × 100 = 1200
Multiplying by 200, 300, ..., 900

To multiply a number by 200, 300, 400, ..., 900, first multiply the number without 00.
Then, write two zeros (00) to the right of the product.

Examples: (a) 1 × 200 = 200 (b) 12 × 300 = 3600 (c) 14 × 700 = 9800
1 × 2 12 × 3 14 × 7

Think Tank Critical Thinking

Which pair of numbers best completes the given multiplication fact × 100 =

● 65 and 650 ● 10 and 1000 ● 7 and 70 ● 1 and 101

practice time 4E

1. Fill in the blanks.

(a) _____ × 10 = 1000 (b) 6 × 100 = _____ (c) 7 × _____ = 3500

(d) _____ × 3 = 2100 (e) _____ × 60 = 480 (f) 11 × 60 = _____

(g) 5 × 20 = _____ (h) 8 × _____ = 320 (i) _____ × 20 = 120

2. Multiply the following by expanding the bigger number.

(a) 96 × 9 (b) 89 × 5 (c) 36 × 4
(d) 56 × 9 (e) 64 × 8 (f) 82 × 6

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