Page 210 - Math Genius C4

E:\Working\Orange_Education\Math_Genius_4\Open_Files\Chap-11
\\September 30, 2025 12:00 PM Bharat Arora P-9 Reader _________________________ Date: ___________________74

Practice time 11d

1. Convert the following:

(a) 6 hours into minutes (b) 8 hours 30 minutes into minutes
(c) 5 hours into seconds (d) 18 minutes into seconds

(e) 28 minutes 15 seconds into seconds (f) 14 hours 48 minutes into seconds

2. Convert the following:
(a) 216 seconds into minutes and seconds.

(b) 2448 seconds into minutes and seconds.

(c) 3860 seconds into hours, minutes and seconds.
(d) 120 minutes into hours.

addition and suBtRaction of time

To add or subtract the measures of time, we arrange the hours, minutes and seconds in
their columns and then add or subtract. We also regroup the units whenever required.
example 1: Add 28 minutes 32 seconds and 24 minutes 42 seconds.

Solution: Write the time in columns and then add by
following the given steps. When the number of seconds is
Step 1: Add the seconds. greater than 60, regroup seconds
into minutes and seconds.
32 seconds + 42 seconds = 74 seconds

74 seconds = 60 seconds + 14 seconds min sec
= 1 minute 14 seconds 1

Step 2: Add the minutes. 28 32
1 + 28 + 24 = 53 minutes + 24 42
Thus, the sum is 53 minutes 14 seconds. 53 14

example 2: Add 16 hours 24 minutes 18 seconds and 31 hours 48 minutes 52 seconds.
Solution: Step 1: Add the seconds.

18 seconds + 52 seconds = 70 seconds
= 60 seconds + 10 seconds When the number of
minutes is greater than
= 1 minute 10 seconds 60, regroup minutes into

Step 2: Add the minutes. hours and minutes.
1 minute + 24 minutes + 48 minutes = 73 minutes h min sec

= 60 minutes + 13 minutes = 1 hour 13 minutes 1 1
Step 3: Add the hours. 16 24 18
1 + 16 + 31 = 48 hours + 31 48 52

Thus, the sum is 48 hours 13 minutes 10 seconds. 48 13 10

208 Mathematics-4