RRB NTPC - Clocks and Time

1.

My watch gains 5 min every hour. How many degrees the second hand moves in every min? 

   A.) 360º
   B.) 390º
   C.) 430º
   D.) 370º

Answer: Option 'B'

390º

2.

A clock is set right at 5am the clock loses 16min in 24 hours. What will be the right time when the clock indicates 10am? On the 4th day? 

   A.) 10.30pm
   B.) 11pm
   C.) 10.45pm
   D.) 11.15pm

Answer: Option 'B'

Time from 5am. On a day to 10pm. on 4th day = 89 hours. 
Now 23 hrs 44 min. of this clock = 24 hours of correct clock 
365/15 hrs of this clock = 24 hours of correct clock 
89 hrs of this clock = ( 24 × 15/356 × 89) hrs of correct clock
= 90 hrs of correct clock. 
So, the correct time is 11pm. 

3.

At what time between 5.30 & 6 will the hands of a watch be at right angle? 

   A.) 43 7/11 min past 5
   B.) 41 2/11 min past 5
   C.) 42 min past 5
   D.) 44 1/11 min past 5

Answer: Option 'A'

At 5 o'clock, the hands are 25 min. spaces apart. 
To be at right angles and that too between 5.30 and 6, the minute hand has to 
gain 55min. spaces are gained in 60min.
4min. spaces are gained in (60/55 × 40) min. = 43 7/11min. 
Required time = 43 7/11min.past 5.

4.

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

5.

How many times in a day the hands of a clock are straight?

   A.) 22
   B.) 21
   C.) 43
   D.) 44

Answer: Option 'D'

In 12 hours, the hands coincide or are in oppesite direction 22 times. 
In 24 hours, they are at right angles 22 times.

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