That was not long ago. Grandpa and I took the No.2 bus to the Youth Palace. Just as the bus was about to leave, 1 the bus just started at the same time as us. At this time, grandpa looked at the two cars in front and suddenly smiled and said to me, "Grandpa has a question to test you, okay?" I answered confidently: "OK!" "Then listen carefully. If the 1 bus runs every 3 minutes and the No.2 bus runs every 5 minutes, how many minutes does it take for the two cars to leave at the same time? " I paused and said, "Grandpa, your question still needs one condition: the starting point of bus 1 and the starting point of bus 2 are in the same place." Grandpa listened to my words, suddenly patted his clever bald head and said with a smile, "I was very confused at that time, and my questions were not rigorous enough, but Zequn thought very well." Grandpa and I laughed happily. At this time, my grandfather said, "well, now let's assume that it is the same starting point." What do you think is the solution? " 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 (3×5= 15), so 15 is their least common multiple, that is, it takes at least 15 minutes for two cars to start at the same time. " Grandpa praised me: "correct answer!" 100 points. " Yeah! Listen to grandpa. I raised my hands happily.
In this case, I understand a truth: mathematical knowledge is really everywhere in real life.