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)... / _ \