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Mathematics>Standard Multiple Choice

Read the following SAT test question and then click on a button to select your answer.

For every 10 dollars Ken earns mowing lawns, he gives 3 dollars to his younger brother, Tim, who helps him. Which of the following gives the relationship between d, the number of dollars Ken earns, and t, the number of dollars he gives to Tim?

(A) d=(3t)/10
(B) d=(10t)/3
(C) d=3/(10t)
(D) d=10/(3t)
(E) d=(3t)-10

答案和解析

答案：B

解析：

For every 10 dollars Ken earns, he gives 3 dollars to Tim. Thus if Ken earns d dollars and gives Tim t dollars, the proportion d/t=10/3 holds. Multiplying both sides of this proportion by t gives d=(10t)/3.