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Practice Time 9A

1. Choose the correct option.

( a) 9:15 p.m. in the 24-hour clock is:
( i) 2115 hours (ii) 2015 hours (iii) 1815 hours (iv) 2315 hours

( b) 2155 hours in the 12-hour clock is:
( i) 21:55 a.m. (ii) 21:55 p.m. (iii) 9 : 55 p.m. (iv) 9 : 55 a.m.

2. Convert the following 24-hour clock time into 12-hour clock time using a.m., p.m.

( a) 0320 hours (b) 0428 hours (c) 0937 hours (d) 1429 hours
( e) 1330 hours (f) 1740 hours (g) 1825 hours (h) 0000 hours
( i) 2222 hours (j) 2138 hours (k) 1348 hours (l) 2000 hours

3. Convert the following 12-hour clock time into 24-hour clock time.
( a) 1:40 a.m. (b) 4:57 a.m. (c) 12:06 a.m. (d) 6:05 a.m.

( e) 10:24 a.m. (f) 7:36 p.m. (g) 12:15 p.m. (h) 2:17 p.m.
( i) 11:00 p.m. (j) 12:00 midnight (k) 3:30 p.m. (l) 9:40 p.m.

COnvERsiOn Of TimE

The relationships between different units of time given below help you convert between them.

1 minute = 60 seconds 1 month = 30 days

1 hour = 60 minutes 1 year = 12 months
1 day = 24 hours 1 year = 365 days

1 week = 7 days 1 leap year = 366 days
Conversion of Higher Units into Lower Units

To convert higher units of time into lower units, we multiply.
Example 1: Convert the following:

( a) 15 minutes into seconds Knowledge Desk Cross-Curricular Learning
( b) 8 minutes 52 seconds into seconds A leap year has 366 days. Julius

( c) 2 hours 23 minutes 19 seconds into seconds Caesar introduced the first calendar
leap year in 46 B.C. The Earth
Solution: takes exactly 365 days, 5 hours,
48 minutes and 45 seconds to move
( a) 1 minute = 60 seconds around the Sun.

So, 15 minutes = (15 × 60) seconds = 900 seconds.

( b) 8 minutes 52 seconds = 8 minutes + 52 seconds
= (8 × 60) seconds + 52 seconds

= 480 seconds + 52 seconds = 532 seconds

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