How to write this question How to write this question.

Hello, classmates:

This question needs to consider two different colors of bricks, which are analyzed as follows;

Question 1: According to the observation, the number of triangular tiles in the picture is ....，4=22；9=32；16=42；…From this, it can be concluded that the total number of positive tiles of the nth graphic tile is (n+1)2.

The second question: from the question, the two bricks are of the same type and size; From the figure, it can be seen that the white bricks grow three times, that is, in the nth figure, the white bricks are (3n), and it can be observed from the figure that the triangle is an equilateral triangle, and the black brick grows into an equal difference series with a tolerance of 3, that is, in the nth figure, the black brick is (1+2+3+...+n), when n=20, 1+2+3+....+20 = 210 (block).

A: The number of black tiles in the 20th figure is 210

1) According to the observation, the number of triangular black tiles in the picture is 1, 3, 6, 10, 15...From this, it can be concluded that the total number of positive blocks of the nth graphic paving black tile is n(n+1) 2 pieces.

The number of triangular white tiles in the picture is 3, 6, 10, 15....From this, it can be concluded that the total number of positive blocks of the nth graphic paving tile is (n+1) (n+2) 2.

Therefore, it can be concluded that the positive total number of tiles of the nth graphic tile is [n(n+1)+(n+1)(n+2)] 2=(n+1) 2=n 2+2n+1 (block).

2) The total number of positive blocks of black tiles paved by the nth figure of question 1 is n(n+1) 2 pieces.

It can be seen that when n=20, 20(20+1) 2=210 (blocks) Answer: The number of black tiles in the 20th figure is 210

；2:239；

4: 4090 times 10; We can communicate again, welcome to adopt.

The radius is 8 meters, plus the width of the path is 2 meters, which is 10 meters, so the total area = 10 times 10 - 8 times 8 = 36

So the answer is 36 square meters.

The number of farmers is 90 (50-45) = 45 people, and the lamb **45 * 50 = 2250 yuan.

There are x farmers, and one sheep ** is y

45x+90=y

50x=y finds x=18

y=900

1) 16/56 Respectfully return 21/56

2) 5/18 3/18

Satisfaction is buried