AMC10 2002 A

AMC10 2002 A · Q6

AMC10 2002 A · Q6. It mainly tests Linear equations, Fractions.

Cindy was asked by her teacher to subtract 3 from a certain number and then divide the result by 9. Instead, she subtracted 9 and then divided the result by 3, giving an answer of 43. What would her answer have been had she worked the problem correctly?

老师要求Cindy从某个数中减去3，然后将结果除以9。但她却先减去了9，然后将结果除以3，得到答案43。如果她正确计算，这个答案应该是多少？

(A) 15 15

(B) 34 34

(D) 51 51

(E) 138 138

Answer

Correct choice: (A)

正确答案：（A）

Solution

(A) Let $x$ be the number she was given. Her calculations produce $\frac{x-9}{3}=43$, so $x-9=129$ and $x=138$. The correct answer is $\frac{138-3}{9}=\frac{135}{9}=15.$

（A）设 $x$ 为她被给的数。她的计算得到 $\frac{x-9}{3}=43$，所以 $x-9=129$，且 $x=138$。正确答案是 $\frac{138-3}{9}=\frac{135}{9}=15$。

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