A clock is set right at 7 a.m. It gains 3 minutes in every hour of correct time. What time will the clock show when the correct time is 1 p.m. on the same day?
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → 1:18 p.m.
A clock that gains runs ahead, so it shows the correct time plus the total gain since it was set right.
Correct time passed from 7 a.m. to 1 p.m. \(=6\) hours
Total gain \(=6\times3=18\) minutes
Time shown \(=\) 1:00 p.m. \(+\) 18 minutes \(=\) 1:18 p.m.
Why the other options are incorrect
Option (1) 12:42 p.m. — Incorrect. This subtracts the 18 minutes, as for a clock that loses time.
Option (2) 1:15 p.m. — Incorrect. This counts only 5 hours of gain from 7 a.m. to 1 p.m.
Option (4) 1:21 p.m. — Incorrect. This counts 7 hours by including both 7 and 1 as hours of gain.