A watch which gains uniformly is 2 minutes low 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)3 p.m. on Thursday
(d)1 p.m. on Friday
Answer
Answer (as printed): B
Explanation
Time from 12 p.m. on Monday to 2 p.m. on the following Monday = 7 days 2 hours $=170$ hours. ∴ The watch gains $\left(2+4 \frac{4}{5}\right) \mathrm{min}$. or $\frac{34}{5} \mathrm{min}$. in 170 hrs. Now, $\frac{34}{5} \mathrm{min}$. are gained in 170 hrs. $\therefore 2$ min. are gained in $\left(170 \times \frac{5}{34} \times 2\right) \mathrm{hrs}=50 \mathrm{hrs}$. ∴ Watch is correct 2 days 2 hrs. after 12 p.m. on Monday i.e. it will be correct at 2 p.m. on Wednesday.