AMC8 2003

AMC8 2003 · Q5

AMC8 2003 · Q5. It mainly tests Percent, Arithmetic misc.

If 20% of a number is 12, what is 30% of the same number?

一个数的20%是12，该数的30%是多少？

(A) 15 15

(B) 18 18

(D) 24 24

(E) 30 30

Answer

Correct choice: (B)

正确答案：（B）

Solution

If 20% of the number is 12, the number must be 60. Then 30% of 60 is $0.30 \times 60 = 18$. OR Since 20% of the number is 12, it follows that 10% of the number is 6. So 30% of the number is 18.

如果该数的20%是12，则该数一定是60。那么60的30%是$0.30 \times 60 = 18$。或者因为该数的20%是12，所以10%是6。因此30%是18。

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