I used to think that learning the knowledge of "finding the least common multiple" was boring, and it was really annoying to deal with the problem of "finding the least common multiple of 1 1 2" all day. I have always felt that it is useless to learn this knowledge in my life.

However, one thing changed my view.

That was not long ago. Grandpa and I went to the Youth Palace by bus. My father and I took the No.3 bus and were about to leave when the 1 bus just took us away.

At this moment, grandpa looked at two cars and suddenly smiled and said to me, "Xiao Ying, grandpa has a question to test you, okay?" "I answered with confidence," OK! " "That you listen up, if the 1 bus runs every 3 minutes, then the No.3 bus runs every 5 minutes. How many minutes will it take for these two cars to start at the same time? " After a pause, I said, "Grandpa, you can't solve this problem. "Grandpa looked at me doubtfully." Really? There is still one condition missing in this problem: 1 bus and bus No.3 start at the same place. "

After listening to my words, grandpa suddenly patted his clever bald head and said with a smile, "I am a doctor of mathematics sometimes, and my questions are not rigorous enough, but I will still think carefully." "Grandpa and I smiled happily. Then grandpa said, "OK, now suppose it's the same starting point. How do you solve it? " "I thought about it and blurted out," 15 minutes.

Because 3 and 5 are prime numbers, finding the least common multiple of prime numbers is equal to the product of these two numbers (3х5= 15), so 15 is their least common multiple. In other words, two cars can leave at the same time in at least 15 minutes. Grandpa praised me: "The answer is correct! 100 points. " "Yes!" After listening to grandpa's words, I raised my hand happily. From this incident, I understand a truth: mathematical knowledge is really everywhere in real life.