Page 160 - ICSE Math 5

1
Similarly, to change from a smaller unit to a larger unit, multiply the value by or divide by 10
as many times till you reach that unit. 10
1
For example, to convert 1 cm to dam, multiply the value by thrice or divide it by 1,000.
10
1 1 1 1
1 cm = 1 × × × dam = dam
10 10 10 1000

Expressing length in decimal form

When we convert measures from smaller to larger units, we can express the given measures in
decimals.
1
Since 1 m = 100 cm, we can write 1 cm = m = 0.01 m.
100
1
Similarly, 1 km = 1,000 m and we can write 1 m = km = 0.001 km.
1000
Example 2: Convert the following as directed.
(a) 3 mm to m (b) 179 cm to m
1 1 1
Solution: (a) 3 mm = 3 × × × m m dm cm mm
10 10 10  1  1  1
1 3 10 10 10
= 3 × m = m = 0.003 m
1000 1000
1 1 179
(b) 179 cm = 179 × × cm = cm = 1.79 cm
10 10 100
Example 3: Express 14 km 6 hm 3 dam 7 m in km using decimal notation.
1 1 1
Solution: We know that 1 hm = km, 1 dam = km and 1 m = km.
10 100 1000
6
6 hm = km = 0.6 km Top Tip
10
3
3 dam = km = 0.03 km The decimal point 14 6 3 7.
100 separates km from m

7 other smaller units. km hm dam
7 m = km = 0.007 km
1000

Thus, 14 km 6 hm 3 dam 7 m = 14 km + 6 hm + 3 dam + 7 m
= 14 km + 0.6 km + 0.03 km + 0.007 km
= 14.637 km

So, 14 km 6 hm 3 dam 7 m = 14.637 km.

Exercise 11.1

1. Write the given measures in metres (m) and centimetres (cm).
(a) 2.38 m (b) 0.45 m (c) 38.6 m (d) 125.79 m
(e) 0.85 m (f) 19.24 m (g) 86.42 m (h) 432.69 m

150