Question

A watch which loses time uniformly is 2 minutes slow at noon on Monday and is 4 min. 48 sec fast at 2 p.m. on the following Monday. When was it correct?

• A. 2 p.m. on Tuesday
• B. 2 p.m. on Wednesday
• C. 1 p.m. on Friday
• D. 4 p.m. on Thursday

Answer 1

The correct option is B

2 p.m. on Wednesday

Time from 12 p.m. on Monday to 2 p.m. on the following Monday = 7 days 2 hours =170 hours.

$\therefore$The watch gains $\left(2+4\frac{4}{5}\right)$min. or $\frac{34}{5}$min. in 170 hrs

Now $\frac{34}{5}$ min. are gained in 170 hrs.

$\therefore$It gains 2 mins in $\frac{170\times 2\times 5}{34}$ = 50 hours.

So, the watch was correct at 2 p.m. on Wednesday.