AMC10 2014 B

AMC10 2014 B · Q3

AMC10 2014 B · Q3. It mainly tests Fractions, Ratios & proportions.

Randy drove the first third of his trip on a gravel road, the next 20 miles on pavement, and the remaining one-fifth on a dirt road. In miles, how long was Randy’s trip?

Randy 的行程前三分之一在碎石路上行驶，接下来 20 英里在柏油路上行驶，剩余五分之一在土路上行驶。Randy 的行程总长多少英里？

(A) 30 30

(B) 40 40

(D) 100 100

(E) $\frac{300}{7}$ $\frac{300}{7}$

Answer

Correct choice: (E)

正确答案：（E）

Solution

The fraction of Randy’s trip driven on pavement was $1 - \frac{1}{3} - \frac{1}{5} = \frac{7}{15}$. Therefore the entire trip was $20 \div \frac{7}{15} = \frac{300}{7}$ miles.

Randy 在柏油路上行驶的行程比例是 $1 - \frac{1}{3} - \frac{1}{5} = \frac{7}{15}$。因此整个行程是 $20 \div \frac{7}{15} = \frac{300}{7}$ 英里。

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