Aptitude - Clock - Discussion

Time from 7 a.m. to 4.15 p.m. = 9 hrs 15 min. = 37/4 hrs.

3 min. 5 sec. of this clock = 3 min. of the correct clock.

37/720hrs of this clock = 1 /20hrs of the correct clock.
(Convert into hours in both sides).

(37/720)x 1 hrs of this clock = 1 /20hrs of the correct clock.

1 hrs of this clock = (1 /20)* (720/37) hrs of the correct clock.

(37/4) hrs of this clock = (1 /20)* (720/37)*(37/4) hrs of the correct clock.
i.e. = 9 hrs.

i.e. The correct time of the clock is 4 p.m.

The problem is with the calculation of 9hr 15min=555 minutes. This value is associated with the erroneous clock. You need to convert it for the true clock. As per data, we can write,

3 mins in the true clock equals 3 min 5 seconds (3+5/60 or 37/12 minutes) in erroneous clock. Thus we have

37/12 mins of erroneous clock equals 3 mins of true clock.
1 mins of erroneous clock equals (3*12/37) mins of true clock.
555 mins of erroneous clock equals (3*12*555/37)=540 mins of true clock.

540 minutes = 540/60 hours = 9 hours. The actual time is (7+9) hours = 16 hours = 4P.M.

@Praveen you got simple & sweet logic. My answer was A.
Here it is:

(9*60)+15=540+15=555min.

(555/3)*5=925 seconds=925/60min=15min and 25sec.

4:15pm)-(15min and 25 sec)=3:59:35pm.

35 sec in min= 35/60=7/12min.

59(7/12).

But you got simple one and correct too.
Thanks buddy!

Why do you get 3 mins in every 3mins 5 secs of the time? :(.

Time between 7AM to 4.15PM = 9 hours 15 Minutes = 9+15/60 hours = 9+1/4 hours = ((9*4)+1)/4 hours = (36+1)/4 hours = 37/4 hours.

Now 3 Minutes 5 seconds of this clock = 3 minutes of the correct clock--------(1).

So, by converting above into hours we get,
First we convert into minutes,

3+5/60 = 3+1/12 = ((3*12)+1)/12 = 37/12 ---------(2).

Now we convert above result into Hours, we get 37/12*60 = 37/720 hours.

And on right side of equation 1, 3 minutes after converting into hours becomes 3/60 hours that is 1/20 hours----------(3).

So from equations 1, 2, 3 we get,
37/720 hours of this clock = 1/20 hours of correct clock.

Then 37/4 hours of this clock = (1/20)*(37/4)*(720/37) = 9 hours.
Therefore correct time is 7+9 hours = 16 Hours on 24 clock, that is 4PM on 12 hours clock.

How we got 37/720 ? please tell me any one.

How 37/4 becomes not understood?

Leave all worries guys think practically.

For 3 min 5 sec gain.

Then for 15 min 25 sec, for 1 hour 100 sec i.e. 1.5 min and 10 sec.

For 9 hr 15 min it is 13.5 (i.e. 1.5*9) + 1.5 (i.e. Remaining 10 sec*9).

So totally 13.5+1.5= 15 min gain.

That is 4op o'clock.

3 past 5 seconds = 3 mins. There is no such one in the question.

How you took that one? Can you explain clearly?

For 3 mins 5 sec gain.

i.e for 180 sec clock shows 185 sec.

That means for every hour it's shows 1 min 40 sec more than actual time.

We need to calculate actual time when clock shows 4:15 pm.

Given that time set at 7 am so the difference between 7 to 4:15 is 9:15 hours.

Clock showing us 1 min 40 secs more for every hour then for 9 hours 15 secs it shows 15 mins fast.

So the answer is 4 pm.