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)