Chapter 5 Understanding Elementary Shape Ex 5.2 Solutions
Question - 1 : - What fraction of a clock wise 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
(d) 12 to 9 (e) 1 to 10 (f) 6 to 3
Answer - 1 : -
We may observe that in 1 complete clockwise revolution, the hour hand will
rotate by 360º.
(a) When the hour hand goes from 3 to 9 clockwise, it will rotate by 2 right angles or 180º.
Fraction = 
(b) When the hour handgoes from 4 to 7 clockwise, it will rotate by 1 right angle or 90º.
Fraction= 
(c) When the hour handgoes from 7 to 10 clockwise, it will rotate by 1 right angle or 90º.
Fraction= (d) When the hour handgoes from 12 to 9 clockwise, it will rotate by 3 right angles or 270º.
Fraction=
(e) When the hour handgoes from 1 to 10 clockwise, it will rotate by 3 right angles or 270º.
Fraction= (f) When the hour handgoes from 6 to 3 clockwise, it will rotate by 3 right angles or 270º.
Fraction=
Question - 2 : - Where will the hand of a clock stop if it
(a) Starts at 12 and makes 
of a revolution, clockwise? (b) Starts at 2 and makes of a revolution, clockwise? (c) Starts at 5 and makes 
of a revolution, clockwise? (d) Starts at 5 and makes 
of a revolution, clockwise?
Answer - 2 : -
In 1 complete clockwiserevolution, the hand of a clock will rotate by 360º.
(a) Ifthe hand of the clock starts at 12 and makes of a revolution clockwise, thenit will rotate by 180º and hence, it will stop at 6.
b) If the hand of the clock starts at 2 andmakes of a revolution clockwise,then it will rotate by 180º and hence, it will stop at 8.
(c) If the hand of the clock starts at 5 andmakes of a revolution clockwise,then it will rotate by 90º and hence, it will stop at 8.
(d) If the hand of the clock starts at 5 andmakes of a revolutionclockwise, then it will rotate by 270º and hence, it will stop at 2.
Question - 3 : - Which direction will youface if you start facing
(a) East and make of a revolution clockwise?
(b) Eastand make 
of a revolution clockwise?
(c) Westand make of a revolution anti-clockwise?
(d) Southand make one full revolution?
(Shouldwe specify clockwise or anti-clockwise for this last question? Why not? )
Answer - 3 : -
If we revolve one completeround in either clockwise or anti-clockwise direction, then we will revolve by360º and the two adjacent directions will be at 90º or of a complete revolutionaway from each other.
(a) If we start facingEast and make of a revolution clockwise, thenwe will face the West direction.
(b) If we start facingEast and make of a revolution clockwise, thenwe will face the West direction.
(c) If we start facingWest and make of a revolution anti-clockwise,then we will face the North direction.
(d) If we start facingSouth and make a full revolution, then we will again
face theSouth direction.
In case of revolving by 1complete round, the direction in which we are revolving does not matter. Inboth cases, clockwise or anti-clockwise, we will be back at our initialposition.
Question - 4 : - What part of a revolutionhave you turned through if you stand facing
(a) Eastand turn clock wise to face north?
(b) Southand turn clockwise to face east?
(c) Westand turn clockwise to face east?
Answer - 4 : -
If we revolve one completeround in either clockwise or anti-clockwise direction, then we will revolve by360º and the two adjacent directions will be at 90º or of a complete revolutionaway from each other.
(a) If we start facingEast and turn clockwise to face North, then we have to make of a revolution.
(b) If we start facingSouth and turn clockwise to face east, then we have to makeof a revolution.
(c) If we start facingWest and turn clockwise to face East, then we have to makeof a revolution.
Question - 5 : - Find the number of rightangles turned through by the hour hand of a clock when it goes from
(a) 3 to6 (b) 2 to 8 (c) 5 to 11
(d) 10 to1 (e) 12 to 9 (f) 12 to 6
Answer - 5 : -
The hour hand of a clockrevolves by 360º or 4 right angles in 1 complete round.
(a) Thehour hand of a clock revolves by 90º or 1 right angle when it goes from 3 to 6.
(b) The hour hand of aclock revolves by 180º or 2 right angles when it goes from 2 to 8.
(c) The hour hand of aclock revolves by 180º or 2 right angles when it goes from 5 to 11.
(d) The hour hand of aclock revolves by 90º or 1 right angle when it goes from 10 to 1.
(e) The hour hand of aclock revolves by 270º or 3 right angles when it goes from 12 to 9.
(f) The hour hand of aclock revolves by 180º or 2 right angles when it goes from 12 to 6.
Question - 6 : - How many right angles doyou make if you start facing
(a) Southand turn clockwise to west?
(b) Northand turn anti-clockwise to east?
(c) Westand turn to west?
(d) Southand turn to north?
Answer - 6 : -
If we revolve one completeround in either clockwise or anti-clockwise direction, then we will revolve by360º or 4 right angles and the two adjacent directions will be at 90º or 1right angle away from each other.
(a) If westart facing South and turn clockwise to West, then we make 1 right angle.
(b) If we start facingNorth and turn anti-clockwise to East, then we make 3 right angles.
(c) If we start facingWest and turn to West, then we make 1 complete round or 4 right angles.
(d) If we start facingSouth and turn to North, then we make 2 right angles.
Question - 7 : - Where will the hour handof a clock stop if it starts
(a) From6 and turns through 1 right angle?
(b) From8 and turns through 2 right angles?
(c) From10 and turns through 3 right angles?
(d)From 7 and turns through 2 straight angles?
Answer - 7 : -
In 1 complete revolution(clockwise or anti-clockwise), the hour hand of a clock will rotate by 360º or4 right angles.
1. If the hour hand of a clock starts from 6 and turns through 1right angle, then it will stop at 9.
2. If thehour hand of a clock starts from 8 and turns through 2 right angles, then itwill stop at 2.
3. If thehour hand of a clock starts from 10 and turns through 3 right angles, then itwill stop at 7.
4. If thehour hand of a clock starts from 7 and turns through 2 straight angles, then itwill stop at 7.
