A clock that gains time — Aptitude Question
A clock that gains time: A clock gains 5 minutes every hour. If it is set correctly at 8 a.m., what will it show… Answer and worked solution on CodeKairo.
- Topic: Mathematical Reasoning
- Section: Logical Reasoning
- Difficulty: Medium
- Time target: 60 seconds
Question
A clock gains 5 minutes every hour. If it is set correctly at 8 a.m., what will it show when the correct time is 2 p.m.?
Options
- 2:20 p.m.
- 2:25 p.m.
- 2:30 p.m.
- 2:35 p.m.
Show the answer and the worked solution
Correct answer: C. 2:30 p.m.
Worked solution
- From 8 a.m. to 2 p.m. is 6 hours.
- The clock gains 5 × 6 = 30 minutes.
- It will show 2:30 p.m.
Answer: 2:30 p.m.
The idea
Multiply the gain per hour by the hours elapsed, then add. A losing clock works the same way with a subtraction.
Shortcut. On the 24-hour clock the true time elapsed is 14 − 8 = 6 hours; at 5 minutes an hour the clock is half an hour ahead, so 2:30 p.m.
Common trap. "2:35 p.m." — counting the hour marks 8, 9, 10, 11, 12, 1, 2 as seven hours; seven marks bound only six hours, which gain 30 minutes, not 35.