Page 177 - Math Genius C5

E:\Working\Orange_Education\Math_Genius_5\Open_Files\CHAP_09
\ 08-Oct-2025 Bharat Arora Proof-9 Reader’s Sign _______________________ Date __________

( c) 2 hours 23 minutes 19 seconds

= 2 hours + 23 minutes + 19 seconds
= (2 × 60) minutes + 23 minutes + 19 seconds

= (120 minutes + 23 minutes) + 19 seconds

= 143 minutes + 19 seconds = (143 × 60) seconds + 19 seconds
= 8580 seconds + 19 seconds = 8599 seconds

Example 2: Convert the following:
( a) 10 hours into minutes Knowledge Desk

( b) 8 hours 42 minutes into minutes Why 60? Why are there
60 seconds in a minute and
( c) 3 days 11 hours 30 minutes into minutes 60 minutes in an hour? This
Solution: system comes from the
ancient Babylonians, who used
( a) 1 hour = 60 minutes a base-60 number system (we
use a base-10 system). It’s a
So, 10 hours = (10 × 60) minutes = 600 minutes. mathematical tradition that

( b) 8 hours 42 minutes = 8 hours + 42 minutes is thousands of years old.

= (8 × 60) minutes + 42 minutes
= 480 minutes + 42 minutes = 522 minutes

( c) 3 days 11 hours 30 minutes

= 3 days + 11 hours + 30 minutes
= (3 × 24) hours + 11 hours + 30 minutes ( 1 day = 24 hours)

= (72 hours + 11 hours) + 30 minutes

= 83 hours + 30 minutes

= (83 × 60) minutes + 30 minutes ( 1 hour = 60 minutes)
= 4980 minutes + 30 minutes

= 5010 minutes

Example 3: Convert the following:
( a) 7 days into hours (b) 5 days 18 hours into hours

Solution:
( a) 1 day = 24 hours

So, 7 days = (7 × 24) hours = 168 hours.

( b) 5 days 18 hours = 5 days + 18 hours
= (5 × 24) hours + 18 hours ( 1 day = 24 hours)

= 120 hours + 18 hours

= 138 hours

Mathematics-5 175175
Mathematics-5