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题库 / Prep2007E1-DS-119
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
Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.
Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.
BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.
EACH statement ALONE is sufficient.
Statements (1) and (2) TOGETHER are NOT sufficient.
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做了英文的题，发现自己智商变低了：
总重量不变：z = x + y
x与y兑在一起 总重量不变
主要搞清楚z=x+y
利用恒等量：
0.1x+0.02y=0.05z=0.05(x+y)
(1) y=10
0.1x+0.02*10=0.05(x+10)
(2) z=16, y=16-x
0.1x+0.02(16-x)=0.05*16
1.x+y=z
2.(0.02y+0.1x)/(x+y)=0.05