Question

A watch is a minute slow at 1 p.m. on Tuesday and 2 minutes fast at 1 p.m. on Thursday. When did it show the correct time ?

• A. 1:00 a.m. on Wednesday
• B. 5:00 a.m. on Wednesday
• C. 1:00 p.m. on Wednesday
• D. 5:00 p.m. on Wednesday

Answer 1

The Correct Option is B

To solve the problem, we have the following scenario: the watch was slow by 1 minute at 1 p.m. on Tuesday and fast by 2 minutes at 1 p.m. on Thursday. This indicates a total time span from 1 p.m. on Tuesday to 1 p.m. on Thursday, which is 48 hours.

During this period, the watch moved from being 1 minute slow to 2 minutes fast, resulting in a total inaccuracy change of 3 minutes (from -1 minute to +2 minutes).

The watch corrects itself by 3 minutes over 48 hours. We need to find out when it was showing the correct time. We calculate how long it takes for the watch to adjust itself by 1 minute:

Time for 1-minute correction = 48 hours / 3 = 16 hours.

This means the watch corrects itself by 1-minute every 16 hours. Since the watch was 1 minute slow at 1 p.m. on Tuesday, it will show the correct time exactly 16 hours later:

1 p.m. on Tuesday + 16 hours = 5 a.m. on Wednesday.

Thus, the watch shows the correct time at 5:00 a.m. on Wednesday.