Su story

Professor Su, a famous mathematician from China, went to France for an academic visit. An accompanying mathematician asked Professor Su several questions on the tram.

French mathematician: Hello, Professor Su! May I ask you a question?

Sue: Sure, go ahead!

Fa: It's about the itinerary. Specifically, there is a distance of 50km between A and B, A is at A and B is at B, and both of them start at the same time and walk in opposite directions. A walks 3km per hour and B walks 2km per hour, so how many hours can they meet?

Sue: There are two kinds of travel problems in life, meeting and catching up. You asked a typical chance encounter question. It can be solved well by listing one-dimensional linear equations. You see:

Suppose Party A and Party B meet for x hours.

3x+2x=50 5x=50 x= 10

A: They can meet in 10 hour.

Fa: It's really simple after listening to you.

The French mathematician didn't expect the China people to answer his question so quickly. Then I asked another question.

Method: A puppy runs 5 kilometers per hour. It starts from A, meets B, just visible and runs to A, meets A, just visible and runs to B. How many kilometers did the dog run when A and B met?

Sue: Obviously, the puppy runs back and forth until A and B meet, so the time when the puppy runs is the time when A and B meet, and the problem is solved.

According to the above question, they met after 10 hours, so the dog ran away 10 hours, and * * * ran away.

5×10 = 50km

A: The puppy ran 50 kilometers when A and B met.