Page 98 - Start Up Mathematics_6

Example 5: What fraction of a clockwise revolution does the hour hand of
a clock turn through when it goes from: 11 12 1
10 2
(a) 12 to 6 (b) 3 to 6 (c) 10 to 1 (d) 12 to 9 9 3
1 1 1 3
Solution: (a) (b) (c) (d) 8 4
2 4 4 4 7 6 5
Example 6: Where will the hand of a clock stop if it starts at
1
(a) 3 and makes of a revolution clockwise?
2
1
(b) 1 and makes of a revolution clockwise?
4
3
(c) 8 and makes of a revolution clockwise?
4
Solution: (a) 9 (b) 4 (c) 5

Example 7: Which direction will you face if you start facing
1 N
(a) east and make of a revolution clockwise?
2
1
(b) east and make 1 of a revolution clockwise? W E
2
3
(c) west and make of a revolution anti-clockwise?
4
(d) south and make one full revolution? S
Should we specify clockwise or anti-clockwise for the last part? (NCERT)
Solution: (a) West (b) West (c) North (d) South
No, it is not necessary to specify clockwise or anti-clockwise in the last part as it is
a complete revolution.

Example 8: Find the number of right angles turned through by the hour hand of a clock when it
goes from:
(a) 6 to 12 (b) 4 to 7 (c) 3 to 12 11 12 1
Solution: Looking at the various positions of an hour hand in the reference 10 2
clock, we observe: 9 3

(a) rotation from 6 to 12 makes 2 right angles 8 4
(b) rotation from 4 to 7 makes 1 right angle 7 6 5
(c) rotation from 3 to 12 makes 3 right angles

Example 9: How many right angles do you make if you start facing
(a) south and turn clockwise to east?
(b) north and turn anti-clockwise to west?

(c) east and turn to east?
Solution: (a) 3 right angles
(b) 1 right angle

(c) 4 right angles (clockwise as well as anti-clockwise)

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