The unreliable clock puzzle


The unreliable clock puzzle

Your friend gave you a clock for your birthday,
but unfortunately, it's very unreliable.
This one gains exactly 12 minutes every hour.

It is now showing 10pm and you know that it was correct at midnight, when you set it.

If the clock stopped four hours ago, what is the correct time now?

Click here for Answer

The correct time now is 10:20 PM.

Explanation :
Since the clock gains 12 minutes every hour,
for every 60 minutes the clock give 72 minutes.
Now the clock was correct at midnight and it stopped at 10pm, so it ran for 22 hours.
So to get the real hours of the clock, and to know when it actually stopped,
we need to divide the total minutes clock ran by 72 minutes (for every 60 real minutes).
so 22 x 60 = 1320 (real minutes)
1320 / 72 = 18.333 (18 hours 20 minutes)
Hence the clock stopped at midnight + 18hour 20 minutes = 6:20 PM.
Now since the clock stopped 4 hours ago,
the correct time now is 10:20 PM.