Problem:
The clock in Sri's car, which is not accurate, gains time at a constant rate. One day as he begins shopping he notes that his car clock and his watch (which is accurate) both say noon. When he is done shopping, his watch says and his car clock says . Later that day, Sri loses his watch. He looks at his car clock and it says . What is the actual time?
Answer Choices:
A.
B.
C.
D.
E.
Solution:
Starting from noon, after minutes of time elapsed, the car clock went minutes ahead. Therefore, for every minute the car clock goes ahead, minutes of actual time pass by. From the time to , the car goes ahead minutes. Therefore, in terms of actual time, minutes, or hours, of actual time have passed by. If we start at and hours pass by, the time is . Thus, is the correct answer.
Answer: .
The problems on this page are the property of the MAA's American Mathematics Competitions