Current location - Training Enrollment Network - Mathematics courses - The seventh grade mathematics is light and negative and efficient. The answer to p721.2.3.4.5.9.10.1.12.13 is online, etc.
The seventh grade mathematics is light and negative and efficient. The answer to p721.2.3.4.5.9.10.1.12.13 is online, etc.
1.B2。 C3 B 4.28 yuan

5.7.6 hours

9.C

10. 160 yuan

1 1. solution: let this batch of parts have x pieces.

x/ 100-x/( 100+ 10)= 2

( 1 1- 10)/ 1 100×X = 2

X=2200

2200÷ 100=22 (days)

12. Solution: Let it fill in x minutes.

x×(( 1/45)+( 1/60)+( 1/90))= 1

( 1/20)X= 1

X=20

13.( 1) solution: let the first set of costs be x yuan. Suppose: the cost of the second set is Y yuan.

( 1+20%)X = 168( 1-20%)Y = 168

1.2X = 168 0.8Y = 168

X= 140 Y=2 10

(2) (140+210)-168× 2 =14 (yuan)