Question

Two trains are approaching each other from opposite directions with the speeds 10 miles per hour and 20 miles per hour, and heading for a collision. If they are a quarter mile apart, how long will it take for them to collide?

A. 45 seconds
B. 20 seconds
C. 30 seconds
D. 40 seconds
E. 1 minute

Answer 1

When adding the speeds of both trains approaching each other at 10 mph and 20 mph, they have a combined speed of 30 mph. Converting this to miles per minute and calculating the time to cover a quarter mile, we find that it will take them 30 seconds to collide.

Step-by-step explanation:

To determine how long it will take for two trains approaching each other to collide, we can simply add their speeds together and then find the time it takes for them to cover the quarter-mile distance between them. In this case, we have Train A moving at 10 miles per hour and Train B moving at 20 miles per hour. The combined speed at which they are approaching each other is 10 mph + 20 mph = 30 miles per hour. To find the time it takes for them to travel a quarter mile (0.25 miles), we use the formula time = distance / speed. Thus, the time is 0.25 miles / 30 miles per hour.

First, we need to convert 30 miles per hour into miles per minute by dividing by 60 (since there are 60 minutes in an hour), which gives us 0.5 miles per minute. The time it takes to collide is therefore 0.25 miles / 0.5 miles per minute = 0.5 minutes or 30 seconds.