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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 ?

Answer :

Reeshabh
Time from 7 a.m. to 4.15 p.m. = 9 hrs 15 min. = [tex] \frac{37}{4} [/tex] hrs.
3 min. 5 sec. of this clock = 3 min. of the correct clock.
=>[tex] \frac{37}{720} [/tex] hrs of this clock = [tex] \frac{1}{20} [/tex] hrs of the correct clock.
=>[tex] \frac{37}{4} [/tex] hrs of this clock = [tex] \frac{1}{20}* \frac{720}{37}* \frac{37}{4} [/tex] hrs of the correct clock.
= 9 hrs of the correct clock.
Thus, the correct time is 9hrs after 7 a.m. i.e. 4 p.m.
queenelsa
Time from 7 a.m. to 4.15 p.m. = 9 hrs 15 min. =  hrs.
3 min. 5 sec. of this clock = 3 min. of the correct clock.
=> hrs of this clock =  hrs of the correct clock.
=> hrs of this clock =  hrs of the correct clock.
= 9 hrs of the correct clock.
Thus, the correct time is 9hrs after 7 a.m. i.e. 4 p.m.

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