Question

one morning, Lee left home without taking his schoolbag. Then after Lee had walked 900 meters, his mother took his schoolbag and chased him by bike at 170 m/min. If Lee walked at 80 m/min, how soon in minutes could his mother catch him?

Answer 1

Lee's mother will catch him in 10 minutes by biking at a relative speed of 90 m/min, given Lee's 900-meter head start and his walking pace of 80 m/min.

Step-by-step explanation:

Lee's mother needs to catch up to him after he walks 900 meters without his schoolbag. To calculate how soon she can catch him, we'll use the relative speeds of Lee and his mother. Lee walks at 80 m/min, and his mother bikes at 170 m/min. The difference in their speeds is 90 m/min (170 m/min - 80 m/min), which is the speed at which the mother is catching up to Lee.

Since Lee already has a 900-meter head start, we divide this distance by the relative speed of the mother to find out how long it will take her to catch up to him.

The time it will take for Lee's mother to catch him is calculated as follows:
Time = Distance / Relative Speed = 900 meters / 90 m/min = 10 minutes.

Thus, it will take Lee's mother 10 minutes to catch up to him with his school bag.