Discussion :: Clock
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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:
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A.
59\( \frac {7 } { 12 }\)min. past 3 |
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B.
4 p.m. |
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C.
58\( \frac {7 } { 11 }\)min. past 3 |
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D.
2\( \frac {3 } { 11 }\)min. past 3 |
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Answer : Option B
Explanation :
Time from 7 a.m. to 4.15 p.m. = 9 hrs 15 min. =\(\frac { 37 } {4 }\)hrs.
3 min. 5 sec. of this clock = 3 min. of the correct clock.
\(\frac { 37 } {720 }\)hrs of this clock =\( \frac { 1 } { 20 } \)hrs of the correct clock
\(\frac { 37 } {4 }\)hrs of this clock=[\( \frac { 1 } { 20 } \)x\(\frac { 720 } {37}\)x\(\frac { 37 } {4 }\)]hrs of the correct clock
= 9 hrs of the correct clock.
The correct time is 9 hrs after 7 a.m. i.e., 4 p.m.
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