Aptitude - Clock - Discussion

3 min = 3+ 5/60 min = 3+1/12 = 37/12 min.

quarter past = 15 min.

7am-4:15pm = 9hr 15 min= 9 x 60+15=555min.
for 37/12 min = 3 min,
for 555min = ?
540min.

540/60 = 9hr,
7am + 9h = 4pm.

If the clock gains 5sec for every 3mins it travels 9hrs and 15mins i.e., 9.25hrs.
Let the actual clock goes 'x' 3mins.

Then the clock which gains 5 secs for every 3 mins will go (3mins)x + (5secs)x =9.25hrs
=> (3+ (5/60))x = 9.25*60.
So x= 180mins,
i.e., x=3hrs,
So the actual clock goes 3x i.e., 9hrs.
So, 9hrs from 7 a.m. is 4 p.m.

Watch gain 5 sec each 3min.

1-hour watch gain 100sec.

100x9 =900 further 15 min watch gain 25sec if we divided 925/60 we get 15 min we minus 15 min from 4.15 we get 4.00.

I think 59 (7/12) past 3.

So, Option A is correct.

It gains 5 seconds in 3 minutes.

3min = 5seconds
3min = 1/12 min
1min = 1/36 min

Let correct watch shows time which is x min ahead of 7 am.

Then minutes gained by faulty clock = x/36minutes.

So, the faulty clock is ahead of 7 am by (x + x/36)min or 37x/36 min.

but in question, it is given faulty clock shows 4.15 pm which is (9*60+15)min or 555min ahead of 7 am.

So,
37x/36 = 555

x = 540min or 9 hrs

So, the correct time is 7 am + 9hr = 4 pm.

Note: We have to calculate the time gained by the faulty clock in terms of the correct clock not in terms of the faulty clock time given in the question

Thank you everyone for explaining the answer.

Crt time: 3mins wrong time: 3mins 5 seconds.
So 1 hr = 1hr 100 seconds wrong time.
7:00 Am to 4:15 PM = 9 hrs 15 mins difference,
For 9 hr 15 mins = 9 hr 925 sec wrong time,
Subtract 925 sec (900sec = 15 mins)from 4: 15 PM

So, the ANSWER is 4:00 PM.

Clock gains 5 seconds every 3 minutes = 100 seconds every hour (60 minutes) = 900 seconds every 9 hours = 15 minutes every 9 hours.

Hence, when the faulty clock shows 4:15 PM, the actual clock should show 15 minutes less i.e. 4:00 PM.

To: Nitin

You are wrong. The given answer is correct. Don't get confused.

Let me explain in simple manner:

Error Clock :: Original Clock

3 min 5 sec :: 3 min

185 sec :: 180 sec

[9 hr 15 min = 555 min = 33300 sec]

33300 sec :: (180/185 x 33300) sec

33300 sec :: 32400 sec

333000sec = 9 hrs 15 min :: 32400 sec = 9 hrs [:. 32400/3600 = 9]

So,
Time passed by Error clock = 9 hrs 15 min.
Time passed by Original clock = 9 hrs.

Therefore, 9 hrs after 7 am is 4 pm.


Note: What was wrong in Nitin's explanation?

555/3 <--- Problem is here.

It should be

555 min/3 min 5 sec [or] 33300/185

Please think twice before solve problem. Hope this will help you. All the best!

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.