PSAT Math Multiple-Choice Question 540: Answer and Explanation

Question: 540

Which of the following formulas can Maria use to determine the number of kilowatt-hours of electricity she needs to power her cell phone for a certain number of minutes?

• A. n = pm
• B.
• C.
• D. n = p + m

Correct Answer: B

Explanation:

B

The question asks for an equation in terms of a specific variable. Although there are variables in the answer choices, plugging in on this question would be difficult given the number of variables. Instead, solve for n. To begin to isolate n, multiply both sides of the equation by n to get np = m. Divide both sides by p to get . The correct answer is (B).