Page 168 - Start Up Mathematics_6

Using Decimals in Real Life
We use decimals very commonly, while denoting a sum of money, length or mass.

Money

For buying or selling, we need to use currency notes or coins. The Indian currency is rupees and
its symbol is `.
We know that 100 paise is equal to 1 rupee. To convert rupee into paise, we multiply the number
of rupees by 100 and to convert paise into rupees we divide paise by 100.
i.e., 100 paisa = ` 1
1
and 1 paisa = ` or 1 paisa = ` 0.01
100
Length
The standard unit of measuring length is metre.

We know that 100 centimetres makes 1 metre. To convert metre into centimetres, we multiply by
100 and to convert centimetres into metre, we divide by 100.
i.e., 100 cm = 1 m

and 1 cm = 1 m or 1 cm = 0.01 m
100
Mass
In metric system, heavy objects are measured in kilogram (kg) and lighter objects are measured
in grams (g).

We know that 1,000 grams make 1 kilogram. To convert kilogram into grams, we multiply by
1,000 and to convert grams into kilogram, we divide by 1,000.

i.e., 1,000 g = 1 kg
1
1 g = kg or 1 g = 0.001 kg
1,000

While dealing with money, length or mass, we must ensure the data should be in same units. In questions
where different units are used for the same entity, we first convert them into same units and then proceed
further.

Example 20: Express as rupees using decimals.
(a) 15 paise (b) 90 paise (c) 220 paise (d) 50 rupees 60 paise
15 90
Solution: (a) 15 paise = ` = ` 0.15 (b) 90 paise = ` = ` 0.90
100 100

220 60
(c) 220 paise = ` = ` 2.20 (d) 50 rupees 60 paise = ` 50 + ` = ` 50.60
100 100

Example 21: Express as metres using decimals.
(a) 20 cm (b) 429 cm (c) 1,000 cm (d) 6 m 54 cm

20 429
Solution: (a) 20 cm = m = 0.20 m (b) 429 cm = m = 4.29 m
100 100

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