Page 330 - Math Smart - 7

15.1.2 Converting between units of time

You have learnt to tell time in hours (h) and minutes (min). The second(s) is a unit
used to tell very small amounts of time. How are these units related?

1 hour (h) = 60 minutes (min) 1 min = 60 seconds (s)

Example 2

Convert the following to minutes.
a)2h b) 4 h 20 min c) 11 h 45 min

Solution
a) 2 h = 2 X 60 b) 4 h = 4 X 60
= 120 min = 240 min
4 h 20 min = 240 + 20
= 260 min

(c) 11 h = 11 X 60
= 660 min
11 h 45 min = 660+ 45
= 705 min

Example 3

Convert the following to seconds,
a) 3 min b) 5 min 4 c) 20 min 10 s
s
Solution
a) 3 min = 3 x 60 b) 5 min = 5 x 60
= 3 X 6 X 10 = 300 min
= 18 X 10 5 min 4 s = 300 + 4
= 180 s = 304s
c) 20 min = 20 x 60
= 1200 s
20 min 10 s = 1200+ 10
= 1210s

Convert
a) 420 min to h, b) 3000 s to min,
c) 400 min to h and min, and d) 725 sto min and s.

Solution
When converting minutes
to hours, or seconds to a) 420 min = 420+ 60 b) 3000 s = 3000 + 60
minutes, we divide by 60. = 420 + 6 + 10 = 50 min
= 70 + 10
= 7h

Measuring Time, Area, Perimeter and Volume