Multiple choice

A clock which gains uniformly is 2 minutes behind at noon on Monday and is 4 minutes and 48 seconds ahead at 2 p.m. on the following Monday. When did it show the correct time?

  1. 2 p.m. on Tuesday

  2. 2 p.m. on Wednesday

  3. 3 p.m. on Thursday

  4. 1 p.m. on Friday

Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The clock gains 2 + 4.8 = 6.8 minutes in 7 days + 2 hours = 170 hours. It needs to gain 2 minutes to show the correct time. Time taken = (2 / 6.8) * 170 hours = 50 hours. 50 hours from Monday noon is Wednesday 2 p.m.

AI explanation

The total time elapsed is 170 hours, during which the clock gains a total of 6 minutes and 48 seconds. Converting this to seconds gives a total gain of 408 seconds over 170 hours. By dividing 408 by 170, we find the clock gains exactly 2.4 seconds per hour. To find when it showed the correct time, we divide the initial 120-second delay by the 2.4 seconds gained per hour, resulting in exactly 50 hours after noon on Monday. Adding 50 hours to noon on Monday brings us to 2 p.m. on Wednesday. The result is 2 p.m. on Wednesday.