Olympiad Maths Prep

Track / Stage 3 / 133 of 260 #133 of 2000

Problem 133

AMC 10/12, early questions
Algebra Difficulty 3.4 Find the answer

If xx cows give x+1x+1 cans of milk in x+2x+2 days, how many days will it take x+3x+3 cows to give x+5x+5 cans of milk?
(A) x(x+2)(x+5)(x+1)(x+3)(B) x(x+1)(x+5)(x+2)(x+3)(C) (x+1)(x+3)(x+5)x(x+2)(D) (x+1)(x+3)x(x+2)(x+5)(E) none of these\textbf{(A) }\frac{x(x+2)(x+5)}{(x+1)(x+3)}\qquad \textbf{(B) }\frac{x(x+1)(x+5)}{(x+2)(x+3)}\qquad\\ \textbf{(C) }\frac{(x+1)(x+3)(x+5)}{x(x+2)}\qquad \textbf{(D) }\frac{(x+1)(x+3)}{x(x+2)(x+5)}\qquad \\ \textbf{(E) }\text{none of these}

Official solution

First, the problem states:

xx cows x+1\qquad x+1 cans x+2\qquad x+2 days
Multiply the current number of cows by x+3x\frac{x+3}{x} to get the number of cows you want, and divide the number of days by the same amount because an increase in cows will cause a decrease in time.

xx+3xx+1(x+2)xx+3x \cdot \frac{x+3}{x} \qquad x+1 \qquad (x+2) \cdot \frac{x}{x+3}
Finally, multiply the current amount of cans by x+5x+1\frac{x+5}{x+1} to get the number of cans you want, and multiply the number of days by the same amount because an increase in cans will cause an increase in time.

xx+3x(x+1)x+5x+1(x+2)xx+3x+5x+1x \cdot \frac{x+3}{x} \qquad (x+1) \cdot \frac{x+5}{x+1} \qquad (x+2) \cdot \frac{x}{x+3} \cdot \frac{x+5}{x+1}
Therefore, our answer is (A) x(x+2)(x+5)(x+1)(x+3)\boxed{\textbf{(A) }\frac{x(x+2)(x+5)}{(x+1)(x+3)}} ~jiang147369

Source: NuminaMath-1.5, licensed Apache-2.0. Statement and solution reproduced as published; topic, difficulty and ordering added by this site.