Decimals
Exercise 8.2
1). Express as rupees using decimals.
(a) 5 paise (b) 75 paise
(c) 20 paise (d) 50 rupees 90 paise
(e) 725 paise
Answer:
(a) 5 paise
1 Rupee = 100 paise
1 paise = 1/100 Rupee
5 paise = 5/100
= Rs 0.05
(b) 75 paise
1 Rupee = 100 paise
1 paise = 1/100 Rupee
75 paise = 75/100
= Rs 0.75
(c) 20 paise
1 Rupee = 100 paise
1 paise = 1/100 Rupee
20 paise = 20/100
= Rs 0.20
(d) 50 rupees 90 paise
1 Rupee = 100 paise
1 paise = 1/100 Rupee
50 rupees 90 paise =50 + 90/100
= 50 + 0.90
= Rs 50.90
(e) 725 paise
1 Rupee = 100 paise
1 paise = 1/100 Rupee
725 paise =700 paise + 25 paise
= Rs 7 + 25/100
= Rs 7.25
2). Express as metres using decimals.
(a) 15 cm (b) 6 cm
(c) 2 m 45 cm (d) 9 m 7 cm
(e) 419 cm
Answer:
(a) 15 cm
1 metre = 100 cm
1 cm = 1/100 metre
15 cm = 15/100
= 0.15 m
(b) 6 cm
1 metre = 100 cm
1 cm = 1/100 metre
6 cm = 6/100
= 0.06 m
(c) 2 m 45 cm
1 metre = 100 cm
1 cm = 1/100 metre
2 m 45 cm = 2 + 45/100
= 2.45 m
(d) 9 m 7 cm
1 metre = 100 cm
1 cm = 1/100 metre
9 m 7 cm = 9 + 7/100
= 9.07 m
(e) 419 cm
1 metre = 100 cm
1 cm = 1/100 metre
419 cm =400 + 19
= 4 + 19/100
= 4.19 m
3). Express as cm using decimals.
(a) 5 mm (b) 60 mm
(c) 164 mm (d) 9 cm 8 mm
(e) 93 mm
Answer:
(a) 5 mm
1 cm = 10 mm
1 mm = 1/10 cm
5 mm = 5/10
= 0.5 cm
(b) 60 mm
1 cm = 10 mm
1 mm = 1/10 cm
60 mm = 60/10
= 6 cm
(c) 164 mm
1 cm = 10 mm
1 mm = 1/10 cm
164 mm =100 + 60 + 4
= 100/10 + 60/10 + 4/10
= 10 + 6 + 0.4
= 16.4 cm
(d) 9 cm 8 mm
1 cm = 10 mm
1 mm = 1/10 cm
9 cm 8 mm =9 + 8/10
= 9.8 cm
(e) 93 mm
1 cm = 10 mm
1 mm = 1/10 cm
93 mm = 90 + 3
= 90/10 + 3/10
= 9 + 0.3
= 9.3 cm
4). Express as km using decimals.
(a) 8 m (b) 88 m
(c) 8888 m (d) 70 km 5 m
Answer:
(a) 8 m
1 km = 1000 m
1 m = 1/1000 km
8 m = 8/1000
= 0.008 km
(b) 88 m
1 km = 1000 m
1 m = 1/1000 km
88 m = 88/1000
= 0.088 km
(c) 8888 m
1 km = 1000 m
1 m = 1/1000 km
8888 m = (8000 + 800 + 80 + 8) m
= 8000/1000 + 800/1000 + 80/1000 + 8/1000
= 8 + 0.800 + 0.080 + 0.008
= 8.888 km
(d) 70 km 5 m
1 km = 1000 m
1 m = 1/1000 km
70 km 5 m = 70 + 5/1000
= 70 + 0.005
= 70.005 km
5). Express as kg using decimals.
(a) 2 g (b) 100 g
(c) 3750 g (d) 5 kg 8 g
(e) 26 kg 50 g
Answer:
(a) 2 g
1 kg = 1000 g
1 g = 1/1000 kg
2 g = 2/1000
= 0.002 kg
(b) 100 g
1 kg = 1000 g
1 g = 1/1000 kg
100 g = 100/1000
= 1/10
= 0.100 kg
(c) 3750 g
1 kg = 1000 g
1 g = 1/1000 kg
3750 g =(3000 + 700 + 50 + 0) g
= 3000/1000 + 700/1000 + 50/1000 + 0/1000
= 3 + 0.700 + 0.050 + 0
= 3.750 kg
(d) 5 kg 8 g
1 kg = 1000 g
1 g = 1/1000 kg
5 kg 8 g = 5 + 8/1000
= 5.008 kg
(e) 26 kg 50 g
1 kg = 1000 g
1 g = 1/1000 kg
26 kg 50 g = 26 + 50/1000
= 26 + 0.050 kg
= 26. 050 kg
