Question

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

a.M. In the afternoon of the same day, when the watch indicated quarter past 4 o'clock, the true time is:

a. 59 7 min. Past 3 12

b. 4 p.M.

c. 58 7 min. Past 3 11

d. 2 3 min. Past 4 11

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 Option B

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

B. 4 PM is the correct answer.

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