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Junior high school intelligence development newspaper mathematics special edition seventh grade people's education edition enhanced edition 39 th answer
The whole chapter of chapter 8 in the second volume of seventh grade mathematics.

Proficiency Test (B) Reference Answer

I. 1. C2 B3 . D4 . D5 . B6 . C7 . b8 . B9 . b 10 . a

Two. 1 1.-2/3 12.-2 13.30, 60, 90 14.25, 13 15.90, 60 65438.

Three. 19.( 1) x = 1 1,y = 1?

(2)x = - 1,y = 1/2,z= 3

20. Suppose the price of a color TV is X yuan and the price of a washing machine is Y yuan. According to the meaning of the question, x- y = 1000.

13%(x+ y)= 390?

solve

x = 2000,

y = 1000?

So, a color TV set

The price is 2000 yuan, and the price of a washing machine is 1000 yuan.

2 1. Let the price of this mineral water in A and B be X yuan and Y yuan respectively. According to the question, it means 10x+6y = 5 1.

12y-8x = 18?

The solution is x = 3,

y = 3.5?

Because 3.5 > 3, so want to

A water supply point is cheaper to buy.

22. From the meaning of the question, 2x+3y = 23,

3x+2y = 22?

The solution is x = 4,

y = 5?

So the values of x and y are 4 and 5, respectively.

4.23. If the speed of the ship in still water is X km/h and the current speed is Y km/h, it is obtained according to the meaning of the question.

x- y = 20,

2/3(x+ y)= 20?

The solution is x = 25,

y = 5?

So, the ship is in still water.

The intermediate speed is 25 km/h, and the water flow speed is 5 km/h.

24. If Beijing dispatches X computers to Wuhan, Y computers to Chongqing, and Shanghai dispatches them to Wuhan (6-x) and Chongqing (8-y).

x+ y = 10,

400x+800y+300(6 x's)+500 (8 y's) = 7600?

The solution is x = 6,

y = 4?

Therefore, 6-x = 0 and 8-y = 4. Therefore, Beijing will dispatch six stations to Wuhan and Chongqing.

Qing 4 station; Shanghai will ship 0 to Wuhan and 4 to Chongqing, with a total freight of 7600 yuan.