In a circuit, two resistors with resistances… | GMAT Sprint

Free Practice Question

PS · Problem Solving

505-555

Algebra

In a circuit, two resistors with resistances a and b are connected in parallel. If R is the combined resistance of these two resistors, then the reciprocal of R is equal to the sum of the reciprocals of a and b. What is R in terms of a and b?

Answer Choices

Correct answer marked below

ab/(a + b)

Correct

a + b

1/(a + b)

(a + b)/ab

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Explanation

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Official Explanation

Official

To find the combined resistance R of two resistors a and b in parallel, we use the formula:

\frac{1}{R} = \frac{1}{a} + \frac{1}{b}

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Comments

RApr 4, 2025

Thank you very much!

NityasriMay 2, 2025

Greatt

JoydeepMar 19, 2025

Great!

LalaApr 6, 2025

thank you taking time to upload it!

GarvitaMay 29, 2024

Greatt

VindhyaApr 13, 2024

Can someone explain it other way?

shengnanJan 22

Thanks!

What this question tests

What it tests

Your ability to manipulate linear and quadratic expressions, substitute unknowns, and solve equations under time pressure.

Common trap

Losing a sign when moving terms across the equals sign, or dividing both sides by a variable that could equal zero.