An ordinary clock becomes 16 minutes fast every day. If it is set right at 9:00 in the morning, then what time will it show at 6:00 in the evening on the same day?
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → 6:06
A clock that gains time at a steady rate gains in proportion to the time that really passes. It was set right at 9:00 in the morning, so at that moment it showed the correct time and had gained nothing.
It gains 16 minutes in 24 hours, so in 1 hour it gains \(\frac{16}{24}=\frac{2}{3}\) minute (40 seconds)
From 9:00 in the morning to 6:00 in the evening, 9 hours really pass
In those 9 hours it gains \(9\times\frac{2}{3}=6\) minutes, so it is now 6 minutes ahead of the correct time
When the correct time is 6:00, a clock 6 minutes ahead shows 6:06