Aptitude - Clock - Discussion

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

@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.

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.

Find the angle between the minute hand and the hour hand if the time 12:20? please give the answer.

Hi, @Mamta

I didn't understand your answer. Please explain it once again.

Thank you very much @Sundar.

@Dedeepya.

We can't go with the process you suggested because;

Let us take the correct time be 'x'.
Now as we already know that 'x' will be lesser than 4 : 15.
Now the mistake in your idea is you are taking x as 4:15 which means in another (4 : 15 - x) the error clock will gain (4 : 15 - x) * 3s, which you are not considering.

Kindly take 'x' instead of 4 : 15 and solve again you will definitely land into a correct answer.

3M = 5s.
60M = 100s.
9H = (9 * 60m) = (9 * 100s) = 900s.
15M = 25s.
900S + 25s = 925s.
925S / 60s = 15.4m.

So, 15.4 is faster.

So reduce the faster value in actual value.

4.15m - 0.15m = 4h.

As given in question we know that.

A watch gains 5 seconds in 3 minutes.

Its means covert 3 min into seconds 4.

(3 x 60) = 180 sec (1 min = 60 sec).

Question tells 5 seconds gain.

It means for 180 sec it will become 180 + 5 = 185 seconds.

Right time is 180 seconds wrong time is 185 seconds.

Difference between true time and wrong time is 7 am to 4. 15 pm is 9 hours 15 min.

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

For 180 - 185.

? - 555.

(180 x 555) /185 = 540 in sec convert into min I. E 540/60 = 4 min.

How is it 37/4 in the first step?