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A watch that gains uniformly, is two minutes slow at noon on Monday and is 4 minutes 48 seconds fast at 2 pm on the following Monday. When was the watch showing the correct time?

Solution

✅ Correct Option: 2

The watch is 2 minutes slow at noon on Monday and 4 minutes 48 seconds fast at 2 pm on the following Monday. The watch gains uniformly (runs faster than actual time at a constant rate).


From noon Monday to 2 pm the following Monday:

Noon Monday to noon next Monday = 7 days = 7×24=1687 \times 24 = 168 hours

Noon next Monday to 2 pm next Monday = 2 hours

Total time = 168+2=170168 + 2 = 170 hours


The watch went from 2 minutes slow to 4 minutes 48 seconds fast.

Total gain by the watch = 22 min +4+ 4 min 4848 sec

Converting to seconds: 22 min =120= 120 seconds, 44 min 4848 sec =288= 288 seconds

Total gain = 120+288=408120 + 288 = 408 seconds


The watch needs to gain 2 minutes (120 seconds) from the starting point to show correct time.

If 408 seconds are gained in 170 hours, then 120 seconds are gained in:

Time needed =120408×170= \dfrac{120}{408} \times 170 hours

=517×170= \dfrac{5}{17} \times 170

=50= 50 hours


Starting from noon Monday, add 50 hours:

24 hours later → Noon Tuesday

48 hours later → Noon Wednesday

50 hours later → 2 pm Wednesday

Therefore, the watch shows the correct time at 2 pm on Wednesday.

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