1. Cross the bridge

There are four people going to walk from the left to the right of the bridge tonight. 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?

Clever insertion of numbers

125 4 3 = 2000

This formula is obviously not equal, but if two numbers 7 are skillfully inserted into the formula, this equation can be established. Do you know where these two numbers 7 should be inserted?

3. Warm seasons

Spring, summer, autumn and winter = spring, summer, autumn and winter

Spring, summer, autumn and winter = spring, summer, autumn and winter

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

4. Broken car going down the mountain

A broken car has to walk two miles, one mile up the hill and one mile down the hill. When it goes uphill, the average speed is 15 miles per hour. How quickly can you reach an average speed of 30 miles per hour on the second mile? Is it 45 miles? You have to think about it!

5. How many eggs does * * * sell?

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?

6. How many people took the exam?

There are six multiple-choice questions on the test paper, and each question has three options. As a result, the marking teacher found that three answers were randomly selected in all the test papers, and the choice of one question was different from each other. How many people will take the exam at most?

answer

1 Answer: First, A and B cross the bridge together, then B is left on the other side, and A returns alone. When A returns, give the flashlight to C and D and let C and D cross the bridge together. When C and D arrive at the other side, give the flashlight to B and ask B to bring it back.

Finally, A and B crossed the bridge together again. Then the required time is: 3+2+ 10+3+3=2 1 min.

Answer to question 2: The formula after inserting numbers is: 172543=20700.

The answer to question 3: Spring = 2; summer = 1； Autumn = 8; Winter =7

Answer to question 4: The average speed of a broken car can't reach 30 mph in any case. Because when the average speed is 30 miles per hour, the total time for the broken car to go up and down the mountain should be115 hours. It took115 hours to climb the mountain. So the average speed of broken cars is less than 30 miles per hour.

Answer to question 5: Mrs. Wang sold 10 eggs.

Answer to question 6: At most 13 people will take the exam.