Question

A watch gains 5 seconds in 3 minutes was set right at 7:00



a.M. In the afternoon of the same day when the watch indicated 4 o'clock the two true time is

Answer 1

Watch gains 5 seconds in 3 minutes or 5 seconds in every 180 seconds.

Time passed in correct clock = 180 seconds

Time passed in faulty clock = 185 seconds.

Given: Time passed in faulty clock = 9 hours and 15 minutes = 9*60*60 + 15*60 = 33300 seconds

Time elapsed in the correct clock = 180/185*33300 = 32400 seconds = 9 hours.

Hence the time in correct clock = 7 + 9 hours = 4 PM

Alternative solution.

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

HÕPÊ ÌT HÊLPS Ū.....