Basic Concept of Clock
In an aptitude test, you will get questions based on concepts of Clock. Wherein the concept is based on movement of Hour hand and Minute hand.
A clock is a complete circle having 360 degrees, which is equally divided into 12 parts i.e. each part is 360/12 = 30°.
The minute hand rotates through 360 degrees to complete round in one hour.
Angle traced by minute hand in 60 min. = 360°.
In 1 minute it covers 360/60 = 6° per minute.
Angle traced by hour hand in 12 hrs = 360°
The hour hand covers 30° in 60 minutes i.e. ½° per minute.
Both the hands of a clock coincide once in every hour.
The hands of a clock will be in straight line but opposite in direction, 22 times in a day.
The hands of a clock coincide 22 times in a day and become straight 44 times in a day.
The hands of a clock are at right angles 44 times in a day.
We will use these concepts while solving problems on clocks.
Practice Quetions For Clock
Q1) An accurate clock shows 8 o'clock in the morning. Through how may degrees will the hour hand rotate when the clock shows 2 o'clock in the afternoon?
A) 154°
B) 170°
C) 160°
D) 180°
Solution:
Q2) A clock is started at noon. By 10 minutes past 5, the hour hand has turned through
A) 145°
B) 152°
C) 155°
D) 140°
Solution :
Q3) At what time between 7 and 8 o'clock will the hands of a clock be in the same straight line but not together?
A) 5(1/11) minutes past 7
B) 5 minutes past 7
C) 5(3/11) minutes past 7
D) 5(5/11) minutes past 7
Solution:
Q4) At what time between 5.30 and 6 will the hands of a clock be at right angles?
A) 44(7/11) minutes past 5
B) 43 minutes past 5
C) 43(7/11) minutes past 5
D) 44 minutes past 5
Solution :
Q5) An accurate clock shows 8 o'clock in the morning. Through how may degrees will the hour hand rotate when the clock shows 2 o'clock in the afternoon?
A. 144°
B. 150°
C. 168°
D. 180°
Solution :
Q6) The reflex angle between the hands of a clock at 10.25 is:
A) 180°
B) 192(1/2)°
C) 195°
D) 192(1/2)°
Solution :
Q7) A clock is started at noon. By 10 minutes past 5, the hour hand has turned through:
A. 145°
B. 150°
C. 155°
D. 160°
Solution :
Angle traced by hour hand in 5 hrs 10 min. i.e.,
Q8) A watch which gains 5 seconds in 3 minutes was set right at 7 a.m. In the afternoon of the same day, when the watch indicated quarter past 4 o'clock, the true time is:
A) 5 PM
B) 4 PM
C) 58(7/11)min. past 3
D) None Of These
Solution :
3 min. 5 sec. of this clock = 3 min. of the correct clock.
37 / 720 hrs of this clock = 3 min. of the correct clock.
=> 37/ 720 hrs of this clock = 1/ 20 hrs of the correct clock.
=> 37 / 4 hrs of this clock = (1/20 x 720/37 x 37/4) hrs of the correct clock
= 9 hrs of the correct clock.
The correct time is 9 hrs after 7 a.m. i.e., 4 p.m.
Q9) At what time between 7 and 8 o'clock will the hands of a clock be in the same straight line but, not together?
A) 5 min. past 7
B) 5 (2/11) min. past 7
C) 5 (3/11) min. past 7
D) 5 (5/11) min. past 7
Solution :
At 7 o'clock, they are 25 min. spaces apart.
Minute hand will have to gain only 5 min. spaces.
55 min. spaces are gained in 60 min.
5 min. spaces are gained in (60/55 x 5)min = 5 (5/11) min.
Required time = 5 (5/11) min. past 7.
Q10) At what time between 5.30 and 6 will the hands of a clock be at right angles?
A) 43 (5/11) min. past 5
B) 43 (7/11) min. past 5
C) 40 min. past 5
D) 45 min. past 5
Solution:
To be at right angles and that too between 5.30 and 6, the minute hand has to gain (25 + 15) = 40 min. spaces.
55 min. spaces are gained in 60 min.
40 min. spaces are gained in (60/55 x 40) min = 43(7/11)min.
Required time = 43 (7/11) min. past 5.
