My watch, which gains uniformly, is 2 min and show at noon on Sunday, and is 4 min 48 seconds fast at 2PM on the following Sunday when was it correct?

A. Wednesday noon
B. Sunday 2 PM
C. Monday noon
D. Tuesday 2 PM

Answer

Correct Answer: D. Tuesday 2 PM


Explanation

At noon on Sunday watch gains 2 Minutes.
And at 2 PM on following Sunday it is 4 Minutes 48 Seconds fast.
So, it gains 6 Minutes 48 Seconds i.e. 2 Minutes + 4 Minutes 48 Seconds (total 408 Seconds) in 170 Hours (Hours from Sunday Noon (12 PM) to following Sunday 2 PM)
Therefore, watch gains 120 Seconds (2 Minutes) in 170*120/408 = 50 Hours
50 Hours = 2 Days 2 Hours
Thus, Watch was correct after 2 days 2 hours from Sunday noon that is Tuesday 2 PM.

A clock loses 5 minutes every hour and was set right at 11 AM on a Monday. When will it show the correct time again?

A. 11 AM on Sunday
B. 11 AM on Monday
C. 11 AM on Tuesday
D. 11 AM on Wednesday

Answer

Correct Answer: A. 11 AM on Sunday


Explanation

As mentioned in Key Point O, the faulty clock will show the correct time when it loses or gains 12 Hours.
In the given problem, the clock loses 5 Minutes in an hour. So, 1 Minute lost in every 12 minutes (60 minutes / 5 minutes = 12 minutes).
Now, for losing 12 hours i.e. 720 Minutes(12 X 60 = 720) it will take 720 X 12 = 8640 Minutes = 144 Hours = 6 Days.
So, Clock will show correct time after 6 days from 11 AM Monday.
Thus, Answer is 11 AM on Sunday.

A watch gain 8 seconds in 4 minutes and was set right at 4 AM. What time will it show at 11 PM on the same day?

A. 11:08
B. 12:38
C. 11:38
D. 12:08

Answer

Correct Answer: C. 11:38


Explanation

8 Seconds in 4 Minutes mean 120 Seconds (or 2 Minutes) in one hour.
From 4AM to 11PM (on the same day) = 19 hours
So, total seconds gain in 19 hours = 19 X 120 (Seconds gain per hour) = 2280 Seconds.
Now, 2280 Seconds = 38 Minutes (i.e. 2280/19 = 38)
Thus incorrect clock will show 11:38PM at 11PM.

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