Aptitude - Clock - Discussion

Can anyone tell me why can't we go with the below process?

For each 3 mins, it gains 5 secs.

So from 7 a.m to 4:15 pm it is 555 mins.

=> It gains 555*5/3 secs or (555*5)/(3*60) mins = 15.425 min.
i.e 15 + 5/12 mins.

So deducting this extra time from 4:15 pm we get 59'7/12 mins past 3.

Please, tell me where I am wrong.

@Manisha.

I hope this will help you.

5 sec gained in 3 min, so,convert 3 min into 1 hr (for convenience).

(5*20)sec gained in (3*20)min.
100 sec gained in 1 hr (60 min=1 hr).
The total duration b/w 7 am to 4.15 pm = 9.15 (9 hr 15 min).

(15 min = 1/4 hr) so, 9.15 = 9 hr + 1/4 hr = 37/4 hrs.

In 1 hr 100 sec gained so, in 37/4 hrs ?
(37/4)*100 = 37*25 = 925 sec.

Convert sec into min:
925 sec = 925/60 min = 15.41 min (approx 15 min).

True time calculation:

Time is to be gained so, clock running fast. To find the true time , we need to subtract 15 min from 4.15.

Then, true time = 4.15 - 15 min = 4 pm.

I can't understand this, please can anyone explain it in a better way?

Hai friends,

I think we have to find the error.
Clock gains 5 sec in 180sec of actual clock.

So,

The error is 5 sec in 185 sec. in errored clock.
In error clock. The passed time is 9H and 15min.

Which is equal to 555 min.(9 * 60 + 15).
Thus it is 33300 in sec.

We have 5 sec error for every 185 sec.
So for 33300 sec we have 900 sec error. (33300 * 5/185).

Error in min. is 15 (900 sec / 60).

So the actual time is 4:00pm (4:15 - 15 min).

I hope you all understood.

@Anandkumar.

Calculation is simple.

3/60 = 1/20.

5/60*60 = 5/3600 = 1/720.

Now add both the values ==> 1/20+1/720 = 37/720.

Hi guys anyone explain about the (3/60) + (5/(60*60)) = 185/3600 = 37/720. Calculation please.

I think the correct option is A. From 7 am to 4:15 pm, number of minutes passed is 555 min. As given for every 3 min it gains an extra 3 seconds.

So 555/3 = 185 min. Therefore 185*(5/60) = 15*5/12, so subtract 4:15 with 15*5/12, we get 59*7/12 min past 3.

In 3 mins clock gains 5 sec.

15 mins -- -- 25 sec.

6o mins --- ----- 100 sec.

Now, from 7 am to 4:15 pm total time = 9 hrs 15 mins.

So, in 9 hrs clock gains = 9*100 = 900 sec.

In 15 mins -- --- = 25 sec.

Therefore, total gain by the clock in these 9 hrs 15 mins = (900/60+25/60) = 15 min 5/12 sec.

Hence correct time will be 59*7/12 min past 3.

Can't understand why 3 min 5 sec corrected to 3:00 min?

How 37/720 is changed to 720/37?