PSAT Math Multiple-Choice Question 626: Answer and Explanation

Question: 626

Machine 1 can manufacture one box in A hours, and Machine 2 can manufacture an identical box in B hours. When working simultaneously, Machines A and B can produce 1 box in T hours. This relationship is given by the following formula:

What is the value of B in terms of the other two variables?

• A.
• B.
• C.
• D.

Correct Answer: A

Explanation:

(A) First, we'll solve for . To do this, subtract from both sides:

Don't be tempted to pick choice (C)! We've solved for , not for B as asked in the question. To solve for B, we must take the reciprocal of what we have:

This matches answer (A).