Aptitude - Clock - Discussion

7am to 4.15pm.
Total 9hrs 15min.

Total time in min= 9*60+15=555min.
For every three min, 5 seconds will be added to the wrong clock
555min /3min= 185 times

So total second added 185*5=925sec,
now convert 925sec to min=925/60= 15 min 25 sec,
so the time in original clock will be 4pm.
555min-15min, =540min=9hrs.
25 sec is neglected because clocks trigger by 5sec only after completing 3mins.

It's given that error clock gains 5 seconds in each 3 minutes of perfect clock.
So, 3min 5sec of error clock = 3min of perfect clock.

Or, [3+(5/60)] min of error clock = 3min of perfect clock. (185s of error clock = 180s perfect clock)
Or, (37/12) min of error clock = 3min of perfect clock
Or 1 min of error clock = 3*12/37 min of perfect clock =36/37.

Now error clock moved from 7am to 4:15pm = 9hr 15min = ( 9*60 + 15 )min = 555min.
So in 555 min of error clock = (36/37)*555 min of perfect clock = 540min of perfect clock.
= (540/60) hr = 9 hr of perfect clock.
So 9hr from 7am is 4pm. Thus the answer is [B] 4 p.m.

There is no coincidence between 11 &12 hence only 11 coincidence per 12 hours.
Totally 22 coincidence per day,
Hence answer is 32.

9 hrs 15 min. = 37/4 hrs? How please explain.

3 mins clock gains 5 sec mean? Please explain it.

@Sundar.

Your explanation is in a very simple way. Thanks.

How to solve 555/60 = 37/4?

Find the ratio 15 sec, 1 min. Please explain this question.

We can also solve it by;

Time from 7 a.m to 4.15 pm is 9hrs and 15 mins.
9hrs is 540 min and 15 min=555 min.
Then, how many 3 min in 555 min=555/3=185.
So, 5 sec is added 185 times.

185*5=925 sec.925 sec can be converted into 15 min(925/60=15.4 @approx 15min).
Watch shows the time at 4:15 pm.
15 min added.so the correct time is 4 PM.

Total 555min,
5 sec for 3 mins,
so total 925 sec increase,
i.e. 15mins 25 sec.
time is 4:15.

So corrected time 3 hrs 59 mins 45 secs.