Page 4 - Lesson Notes

 Moving from 12 to again till 12 clockwise a hour hand makes one complete
revolution i.e. 360°.
 The hour hand turns 360° in 12 hours.
 Note: 12 hours = 1 full revolution

 The hour hand in 1 hour completes = 360 ÷ 12 = 30°.
 Therefore a turn of the hour hand from 6 to 9

o Covers 3 hours = 3 × 30° = 90°
o 12 hours = 1 revolution
1
1 hour = revolution.
12
1
1
3 hour = 3 × = revolution
12 4
1
Therefore a turn of the hour hand from 6 to 9 covers revolution.
4
1
Other way: Therefore a turn of the hour hand from 6 to 9 covers = 90 = revolution.
360 4
Check your understanding: (NCERT, Pg- 91, Exercise – 5.2) (First one is done for you as an
example)

Q1. What fraction of a clockwise revolution does the hour hand of a clock turn through,

when it goes from (a) 3 to 9 (b) 4 to 7 (c) 7 to 10
Answer: (a) By moving from 3 to 9, the hour hand of clock has covered 6 hours.

In 12 hour = 1 revolution is covered.

 In 1 hour = revolution is covered.

 In 6 hours = 6 × = revolution is covered.