RRB NTPC - Clocks and Time

1.

How much does a watch lose per day, if its hands coincide every 64 minutes? 

   A.) 32 8/11min
   B.) 36 5/11min
   C.) 90min
   D.) 96min

Answer: Option 'A'

55 min. spaces are covered in 60 min.
60 min spaces are covered in (60/55 × 60)min = 65 5/11 min
Loss in 64 min = ( 65 5/11- 64 ) = 16/11 min
Loss in 24 hrs = ( 16/11 × 1/64 × 24 × 60 ) min
= 32 8/11 min

2.

How much watch gain or lose per day, If its hands coincide every 64 min’s? 

   A.) Gain 92 min
   B.) Lose 9 min
   C.) Lose 34 5/11 min
   D.) Lose 32 8/11 min

Answer: Option 'D'

55 min. spaces are covered in 60 min. 
60 min. spaces are covered in (60/55 × 60) min = 65 5/11min 
Loss in 64min = (65 5/11 - 64) = 16/11 min 
Loss in 24 hrs= (16/11 × 1/64 × 24 × 60 ) min = 32 8/11 min. 

3.

At what time between 7 & 8 o'clock will the hands of a watch be in the straight line but no together? 

   A.) 5 3/11 min past 7
   B.) 5 5/11 min past 7
   C.) 5 3/11 min past 7
   D.) 43min past 7

Answer: Option 'B'

When the hands of the clock are in the same straight line but not 
togerther, they are 30 minute spaces apart.
At 7 o'clock, they are 25min. spaces apart. 
Minute hand will have to gain only 5 min. 
space 55 min. spaces are gained in 60min.
5min. spaces are gained in ( 60/55 × 5) min = 5 5/11 min. 
Required time = 5 5/11 min. past 7.

4.

An accurate clock shows 8 o'clock in the morning. Through how many degrees will the hour hand rotate  when the clock shows 2 o'clock in the afternoon? 

   A.) 144º
   B.) 150º
   C.) 168º
   D.) 180º

Answer: Option 'D'

Angle traced by the hour hand in 6 hours = ( 360/12 × 11/3 )degrees 
=180º

5.

When the time in the clock is 7.20, then the angle between the hands of the clock is: 

   A.) 100º
   B.) 120º
   C.) 90º
   D.) 110º

Answer: Option 'A'

7:20 
7:4 
7~4 = 3 × 20 = 90 + 10 = 100º 

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