Prep T1-DS-119

[hwatai]

A contractor combined x tons of a gravel mixture that contained 10 percent gravel G, by weight, with y tons of a mixture that contained 2 percent gravel G, by weight, to produce z tons of a mixture that was 5 percent gravel G, by weight. What is the value of x ?

(1) y = 10

(2) z = 16

由題目得知 (0.1x+0.02y) =　5
　　　　　　　x+y　　　　100

1.充份，可得x

2. z就是x+y=16，交叉相乘後100(0.1x+0.02y)=5*16,
　得10x+2y=80
　再配合x+y=16，即可解出x與y，故充份

answer goes to (D)... / _ \