Uses of Decimals

We will learn uses decimals in every day. In daily life we use decimals while dealing with length, weight, volume, money etc.

Use of Decimals while Dealing with Money:

100 paise = 1 rupee;

                   [We know that one paise in one hundredth of a rupee.]

1 paise = \(\frac{1}{100}\) rupee = 0.01 rupee

9 paise = \(\frac{9}{100}\) rupee = 0.09 rupee

21 paise = \(\frac{21}{100}\) rupee = 0.21 rupee

Thus, 8 rupees 15 paise = 8\(\frac{15}{100}\) = 8.15 rupees

10 rupees 5 paise = 10\(\frac{5}{100}\) = 10.05 rupees

We read 6.45 rupees as six rupees 45 paise

16.25 rupees as sixteen rupees 25 paise

Use of Decimals while Dealing with Lengths:

10 mm = 1 cm

Therefore, 1 mm = \(\frac{1}{10}\) cm = 0.1 cm;

                                   [One millimetre is one tenth of a centimetre.]

Therefore, 9 mm = \(\frac{9}{10}\) cm = 0.9 cm

Thus, 4 cm 8 mm = 4\(\frac{8}{10}\) cm = 4.8 cm

13 cm 6 mm = 13\(\frac{6}{10}\) cm = 13.6 cm

We know that 100 cm = 1 m;

                                [One centimetre is one hundredth of a metre.]

1 cm = \(\frac{1}{100}\) m = 0.01 m

2 cm = \(\frac{2}{100}\) m = 0.02 m

10 cm = \(\frac{10}{100}\) m = 0.10 m or 0.1 m

89 cm = \(\frac{89}{100}\) m = 0.89 m

Thus, 4 m 56 cm = 4\(\frac{56}{100}\) m = 4.56 m

18 m 8 cm = 18\(\frac{8}{100}\) m = 18.08 m

1000 m = 1 km

Therefore, 1 m = \(\frac{1}{1000}\) km = 0.001 m;

                                 [One metre is one thousandth of a kilometre.]

Therefore, 8 m = \(\frac{8}{1000}\) km = 0.008 km

18 m = \(\frac{18}{1000}\) km = 0.018 km

356 m = \(\frac{356}{1000}\) km = 0.356 km

Thus, 9 km 426 m = 9\(\frac{426}{1000}\) km = 9.426 km

25 km 693 m = 25\(\frac{693}{1000}\) km = 25.693 km

Use of Decimals while Dealing with Weights:

1000 g = 1 kg

1 g = \(\frac{1}{1000}\) kg = 0.001 kg;

                                 [One gram is one thousandth of a kilogram.]

For examples:

5 g = \(\frac{5}{1000}\) kg = 0.005 kg

49 g = \(\frac{49}{1000}\) kg = 0.049 kg

365 g = \(\frac{365}{1000}\) kg = 0.365 kg

Thus, 7 kg 118 g = 7\(\frac{118}{1000}\) kg

                          = 7.118 kg

20 kg 48 g = 20\(\frac{48}{1000}\) kg

                = 20.048 kg

Use of Decimals while Dealing with Volumes:

1000 ml = 1 l

1 ml = \(\frac{1}{1000}\) l = 0.001 l;

                                 [One millilitre is one thousandth of a litre.]

For examples:

6 ml = \(\frac{6}{1000}\) l = 0.006 l

28 ml = \(\frac{28}{1000}\) l = 0.028 l

146 ml = \(\frac{146}{1000}\) l = 0.146 l

Thus, 5 l 450 ml = 5\(\frac{450}{1000}\) l

                         = 5.450 l

19 l 32 ml = 19\(\frac{32}{1000}\) l

                = 19.032 l

Questions and Answers on Uses of Decimals:

1. Write in decimals. (One has been done for you):

(i) 21 rupees 55 paise → 21.55 rupees

(ii) 250 rupees 5 paise → ....................

(iii) 3 cm 9 mm → ....................

(iv) 4 km 314 m → ....................

(v) 17 kg 50 g → ....................

(vi) 3 rupees 10 paise → ....................

(vii) 12 m 32 cm → ....................

(viii) 20 m 8 cm → ....................

(ix) 26 km 19 m → ....................

(x) 10 l 70 ml →....................

Answer:

1. (ii) 250.05 rupees

(iii) 3.9 cm

(iv) 4.314 km

(v) 17.05 kg

(vi) 3.10 rupees

(vii) 12.32 m 

(viii) 20.08 m

(ix) 26.019 km

(x) 10.07 l

4th Grade Math Activities

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