Page 106 - ICSE Math 5

Exercise 7.4

Solve the following word problems.

(a) Vandit is practicing for an athletic event. He runs 3 km 750 m in the morning and 2 km
250 m in the evening. How much distance does he run in a day?
(b) Rahul is playing throwball with his friends. In his first attempt, the ball goes at a distance
of 17.5 m while in the second attempt it goes at a distance of 16.75 m. How much farther
does the throwball go in the first attempt?

(c) It rained 3.5 cm on Monday, 2.25 cm on Tuesday and 1.75 cm on Wednesday. How much
did it rain on all the three days?
(d) The thickness of three books are 3.8 cm, 1.06 cm and 2.32 cm. What is the total thickness
of the books if they are kept one above the other?

(e) Akanksha goes to a market to buy sugar. Shop A is selling 1 kg sugar for ` 49.75 and
Shop B is selling 1 kg sugar for ` 45.50. From which shop can she buy sugar to save money?
How much money will she save per kg of sugar?
(f) A carpenter had a 0.9 m long wooden log. He chopped off 0.7 m of the log to use. What
length of the log is left unused?

Multiplication of Decimals

Let’s understand multiplication of decimal numbers with the help of pictures.
0.2 0.2 0.2

+ + =

3 × 0.2 = 0.2 + 0.2 + 0.2 = 0.6
Multiplication of decimals is similar to that of whole numbers with a difference that the decimal
point is placed appropriately.

Multiplication of a Decimal Number by 10, 100 and 1,000

To multiply a decimal number by 10, 100 or 1,000, we shift the decimal point to the right as many
places as the number of zeros in the multiplier.
• To multiply a decimal number by 10, we shift the decimal point one place to the right.
For example, 60.28 × 10 = 602.8
• To multiply a decimal number by 100, we shift the decimal point two places to the right.
For example, 1.134 × 100 = 113.4

• To multiply a decimal number by 1,000, we shift the decimal point three places to the right.
For example, 2.3754 × 1,000 = 2375.4

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