AMC12 2014 A

AMC12 2014 A · Q4

AMC12 2014 A · Q4. It mainly tests Rates (speed).

Suppose that $a$ cows give $b$ gallons of milk in $c$ days. At this rate, how many gallons of milk will $d$ cows give in $e$ days?

假设$a$头奶牛在$c$天产$b$加仑牛奶。以此速率，$d$头奶牛在$e$天产多少加仑牛奶？

(A) \ \frac{bde}{ac} \ \frac{bde}{ac}

(B) \ \frac{ac}{bde} \ \frac{ac}{bde}

(D) \ \frac{bcde}{a} \ \frac{bcde}{a}

(E) \ \frac{abc}{de} \ \frac{abc}{de}

Answer

Correct choice: (A)

正确答案：（A）

Solution

We need to multiply $b$ by $\frac{d}{a}$ for the new cows and $\frac{e}{c}$ for the new time, so the answer is $b\cdot \frac{d}{a}\cdot \frac{e}{c}=\frac{bde}{ac}$, or $\boxed{\textbf{(A) } \frac{bde}{ac}}$.

需要将$b$乘以$\frac{d}{a}$（新奶牛数）和$\frac{e}{c}$（新时间），因此答案是$b\cdot \frac{d}{a}\cdot \frac{e}{c}=\frac{bde}{ac}$，即$\boxed{\textbf{(A) } \frac{bde}{ac}}$。

Topics

AR.007 Rates (speed)