67. A watch which gains 5 seconds in 3 minutes was set right at 7a.m.

1.	67. A watch which gains 5 seconds in 3 minutes was set right at 7a.m. In the afternoon of the same daywhen the watch indicated quarter past 4 o'clock, the true time isA. 3pm3:45pm3:30pm4pm
Answer» Time from 7 am to 4.15 pm = 9 hrs 15 min =37/4hrs 3 min. 5 sec. of this clock = 3 min. of the correct clock. Now 3min.5sec. is37/720hrs of this clock = 3 min.is1/20 hrs of the correct clock 37/4hrs of clock =(1/20×720/37×37/4)hrs of the correct clock. = 9 hrs of the correct clock. The correct time is 9 hrs after 7 am. i.e., 4 pm.

67. A watch which gains 5 seconds in 3 minutes was set right at 7a.m. In the afternoon of the same daywhen the watch indicated quarter past 4 o'clock, the true time isA. 3pm3:45pm3:30pm4pm

Answer»

Time from 7 am to 4.15 pm = 9 hrs 15 min =37/4hrs

3 min. 5 sec. of this clock = 3 min. of the correct clock.

Now 3min.5sec. is37/720hrs of this clock = 3 min.is1/20 hrs of the correct clock

37/4hrs of clock =(1/20×720/37×37/4)hrs of the correct clock.

= 9 hrs of the correct clock.

The correct time is 9 hrs after 7 am. i.e., 4 pm.