1. Two cyclists, 60km apart, are driving towards each other at the speed of10km/h. A bird flew out of one of the cyclists and flew to the other cyclist at a speed of 25km \/ hour. After it met another cyclist, it flew back to the first athlete. It flies around like this. So, what's the total distance the bird flew in the end?

Three hours later, the athletes met, and the bird flew for three hours, 25 times 3, =75KM.

2. Four people cross the bridge, the eldest brother takes 5 minutes, the second brother 10 minutes, the third brother takes 25 minutes and the fourth brother takes 25 minutes. It's midnight, they only have a flashlight, and people who cross the bridge have to send it back. How can they all cross the bridge in half an hour?

Eldest brother and second brother went first, eldest brother sent back the flashlight, third brother and fourth brother passed, second brother sent back the flashlight, and second brother and eldest brother passed together, one *** 1 hour.

3, say a box, there are 1 bacteria, bacteria divide once every minute, and the box is full when it divides 1 hour. Q: If you start putting two bacteria, how long will it take to fill the box?

There are four people, A, B, C and D today, and they have to walk from the left to the right of the bridge at night. Only two people can walk on this bridge at a time, and there is only one flashlight. You must cross the bridge with a flashlight. The fastest time for four people to cross the bridge is as follows: A 2 points; B 3 points; C 8 points; D 10。 Fast walkers have to wait for slow walkers. 2 1 How to cross the bridge?

5. The formula 125 × 4 × 3 = 2000 is obviously unequal, but if two numbers "7" are skillfully inserted into the formula, this equation can be established. Do you know where these two 7s should be inserted?

6. Spring and summer × autumn and winter = summer, autumn, spring and winter, and spring and summer × autumn and winter = spring, summer, autumn and winter. In the formula, spring, summer, autumn and winter represent four different numbers. Can you point out what numbers they represent?

7. A broken car has to walk two miles, one mile uphill and one mile downhill, and the average speed when going uphill is 15 mile. How quickly can you reach an average speed of 30 miles per hour on the second mile downhill? Is it 45 miles?

Mrs. Wang went to the market to sell eggs. The first man bought half the eggs in the basket one after another, and the second man bought the remaining half. At this time, there is an egg left in the basket. How many eggs did Mrs. Wang sell?

9. There are six multiple-choice questions on the test paper, and each question has three options. Results The marking teacher found that when choosing any three answers in all the test papers, the choice of one question was different from each other. How many people will take the exam at most?

10, there is a pasture grass, if you graze 27 cows, you can eat up the grass in 6 weeks; If you graze 23 cows, you can eat all the grass in 9 weeks; If you graze 2/kloc-0 cows, how many weeks can you eat grass?