hours minutes seconds
7 15 30
9 30 40
11 40 32
---------------------------
28 26 42
EXPLANATION: 32 seconds + 40 seconds + 30 seconds = 102 seconds. But,
102 seconds = 1 minute 42 seconds. Write the 42 below and carry the 1
minute. 1 minute (carried) + 15 minutes + 30 minutes + 40 minutes = 86
minutes. But, 86 minutes = 1 hour 26 minutes. Write the 26 and carry the
1 hour. 1 hour + 11 hours + 9 hours + 7 hours = 28 hours. Result = 28
hours 26 minutes 42 seconds.