2016 AMC 12B Problem 1

Below is the professionally curated solution for Problem 1 of the 2016 AMC 12B, from LIVE by Po-Shen Loh. You can also try the full timed exam, view all 2016 AMC 12B solutions, or check the answer key.

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Concepts:exponentorder of operations

Difficulty rating: 920

1.

What is the value of

2a1+a12a \frac{2a^{-1}+\frac{a^{-1}}{2}}{a}

when a=12?a=\tfrac12?

11

22

52\dfrac52

1010

2020

Solution:

With a=12,a=\tfrac12, we have a1=2.a^{-1}=2. The numerator is 22+22=4+1=5,2\cdot2+\dfrac{2}{2}=4+1=5, and dividing by a=12a=\tfrac12 gives 51/2=10.\dfrac{5}{1/2}=10.

Thus, the correct answer is D.

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