Page 52 - Ganit Kaushal

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Ex 1. Draw four situations of revolution on a clock.
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1
Sol. One-fourth revolution = × 360° = 90°. Four situations of one-fourth revolution are as follows:
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Ex 2. What fraction of a clockwise revolution does the hour hand of a clock turn through when it moves
from:
(a) 12 to 6? (b) 1 to 10?
Also, find the number of right angles and degrees turned in each case.
Sol. (a) We know there are 12 equal parts on a clock face.
While moving from 12 to 6, the hour hand covers 6 of these parts.
6 1
∴ Fraction of revolution turned = 12 = 2
1
Number of degrees turned = × 360° = 180°
2
180ϒ
Number of right angles turned = = 2 ( 1 right angle = 90°)
90ϒ
(b) We know there are 12 equal parts on a clock face.

While moving from 1 to 10, the hour hand covers 9 of these parts.
9 3
∴ Fraction of revolution turned = 12 = 4

3
Number of degrees turned = × 360° = 270°
4
270ϒ
Number of right angles turned = = 3 ( 1 right angle = 90°)
90ϒ
Exercise 2.4

1. Find the angle in degrees between the given directions:
(a) N and E (b) S and N (c) S and SE (d) N and SE
2. A boat sailing in the River Ganga is going towards W. If it changes its direction to N, then through
what angle does it turn and in what sense?
3. Raman is standing in his classroom facing his teacher. His teacher is facing South. In which direction
is Raman facing?

4. In the above question, Raman takes a quarter turn in a clockwise sense. In which direction is he facing
now?
5. State the type of angle formed by the following directions in each of the cases given below:

(a) E and W (b) S and SE (c) E and N (d) N and SE
6. At 5 o’clock, what is the degree measure of the angle between the hands of a clock?
7. From 8:00 AM to 10:15 AM, how many right angles does the minute hand of a clock move?

50 Mathematics-6