posted by KeKe on .
8. A mile-long train is moving at 60-miles-per-hour when it reaches a mile-long tunnel. How long does it take the entire train to pass through?
9. How many 3-cent stamps are there in 4 dozen?
it takes the mile-long train 1 minute to pass any fixed point at 60 mph.
So, it takes 1 minute for the front of the train to pass through the tunnel.
At that point, the caboose is just entering the tunnel.
After one more minute, the caboose has exited the tunnel.
Total time: 2 minutes