Page 56 - Start Up Mathematics_7

EXERCISE 3.2

1. Find: (a) 3.34 × 10 (b) 21.567 × 10 (c) 0.0895 × 10

2. Calculate the product:
(a) 13.304 × 100 (b) 221.567 × 100 (c) 0.689 × 100 (d) 3.0895 × 100
3. Evaluate: (a) 123.34 × 1,000 (b) 0.2567 × 1,000 (c) 5.689 × 1,000
4. Find the product:

(a) 2.89 × 17 (b) 21.567 × 11 (c) 3.1009 × 16 (d) 0.00085 × 19
5. Find the product of the given decimal numbers:
(a) 3.03 × 1.09 (b) 1.507 × 12.9 (c) 0.689 × 17.5 (d) 23.08 × 2.3

6. Find the area of a square of side 3.45 m.
7. Find the area of a rectangle of length 12.25 m and breadth 7.35 m.
8. If the cost of 1 kg almonds is ` 325.50, find the cost of 11.9 kg almonds.

Division of Decimal Numbers by 10, 100, 1,000, etc.
We observe, while dividing a decimal number by 10, 100 or 1,000, the digits of the number and
the quotient remains the same but the decimal point in the quotient shifts to the left by as many
places as there are zeros after one, i.e.,

(a) On dividing a decimal by 10, the decimal point is shifted to the left by one place, i.e.,
28.3 ÷ 10 = 2.83.
(b) On dividing a decimal by 100, the decimal point is shifted to the left by two places, i.e.,
28.3 ÷ 100 = 0.283.
(c) On dividing a decimal by 1,000, the decimal point is shifted to the left by three places, i.e.,
28.3 ÷ 1,000 = 0.0283.

Example 15: Find: (a) 372.23 ÷ 10 (b) 62.5 ÷ 10 (c) 0.3 ÷ 10
Solution: (a) 372.23 ÷ 10 = 37.223 (b) 62.5 ÷ 10 = 6.25 (c) 0.3 ÷ 10 = 0.03
Example 16: Find: (a) 740.8 ÷ 100 (b) 33.6 ÷ 100 (c) 0.76 ÷ 100

Solution: (a) 740.8 ÷ 100 = 7.408 (b) 33.6 ÷ 100 = 0.336 (c) 0.76 ÷ 100 = 0.0076
Example 17: Find: (a) 741.3 ÷ 1,000 (b) 0.8 ÷ 1,000 (c) 26.3 ÷ 1,000

Solution: (a) 741.3 ÷ 1,000 = 0.7413 (b) 0.8 ÷ 1,000 = 0.0008 (c) 26.3 ÷ 1,000 = 0.0263
Example 18: Find the equivalent value of each of the following in metres.

(a) 218 mm (b) 120 cm (c) 5.82 km (d) 0.03 km
218 120
Solution: (a) 218 mm = m = 0.218 m (b) 120 cm = m = 1.2 m
1,000 100
(c) 5.82 km = 5.82 × 1,000 m = 5,820 m (d) 0.03 km = 0.03 × 1,000 m = 30 m

Division of a Decimal Number by a Non-Zero Whole Number

In order to divide a decimal number by a non-zero whole number, follow these steps:
Step 1: Divide the decimal number (dividend) by the whole number ignoring the decimal point.

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