400 pieces are distributed in several grids, and each grid can hold at most 1 1 piece. Note: At least 7 squares have the same number of pieces.

Solution: You can put at least 0 blocks in each grid and at most 1 1 block.

0+ 1+2+...+ 1 1=66

So take 66 pieces as a group and place them according to the above rules.

After putting six groups in this way, 1 * * * runs out of 6*66=396 pieces, leaving 4 pieces.

Numbers range from 0 to 1 1, and each number appears six times.

Therefore, no matter how the remaining pieces are placed, the number of pieces with seven squares is the same.

There are many football, basketball and volleyball in the warehouse. There are 50 people in a class to get the ball. It is stipulated that each person should have at least 1 ball and at most 2 balls. How many students have the same number and type of balls?

Solution: According to the regulations, many students have the following nine ways to match the ball:

{ Foot } { Row } { Blue } { Full } { Row } { Blue } { Foot Row } { Foot Blue } { Row Blue }

Nine drawers are manufactured in these nine matching ways.

Think of these 50 students as apples.

=5.5……5

According to the principle of pigeon hole, there are at least six people who hold the same ball.

Note: Choose 26 numbers from 1, 3, 5, …, 99, and the sum of the two numbers must be 100.

These figures are ***50. We can call the number that adds up to 100 logarithmic. If the inverse number of 1 is 99, then these numbers have 25 sets of inverse numbers. Now take 26 of them. Suppose you have 25 numbers. These 25 numbers are not antagonistic. When you take the No.26 bus, you must have taken the wrong number. In other words, when you take 26, you must add two numbers to get 100.