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1. Party A and Party B are running on a 400m long probation track. The speed of Party A is 360m / min, and that of Party B is 240m / min. how many laps did they run together when they first met? How many seconds later did they meet for the first time 2. A and B go out for a walk at the same time from a and B, which are 50 meters apart. A runs 3 meters per second and B runs 2 meters per second. A takes a dog to start with him at the same time. If the dog runs to B at the speed of 10 meters per second, he runs back to a when he meets B, and then he runs back to B when he meets A. when a and B meet, the dog stops and asks how many meters the dog has run? 3. The distance between the two places is 0.4km. A and B start from place C at the same time and walk in opposite directions. A walks to a at the speed of 4km per hour, B walks to B at the speed of 5km per hour, and when a arrives at place a, they catch up with B by bike at the speed of 12km per hour. How long does it take from place C to catch up with B?
1. Let's run for X minutes. So a ran 360x and B ran 240x. A ran one more lap than B. so 360x-240x = 120x = 400. So x = 10 / 3 minutes. So the two ran together: 360x + 240x = 600 * 10 / 3 = 2000 meters. Let's meet in X seconds. 360m / min = 60m / s, 240m / min = 40m / s. so 60x + 40x = 40
One day, my grandfather gave me a math paper. One of the questions was like this: "the 400 meter road is round and good. My classmates and I are going to race. There are ten people in front and ten in back. How many people are in the race?"
Dizzy, isn't 11? Think it should be?
It's 11. In addition to one, because it's round, the remaining 10 can be said to be in the front or behind
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