2006 AMC 10B Problem 12

Below is the professionally curated solution for Problem 12 of the 2006 AMC 10B, from LIVE by Po-Shen Loh. You can also try the full timed exam, view all 2006 AMC 10B solutions, or check the answer key.

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Concepts:substitutionsystem of equations

Difficulty rating: 1140

12.

The lines x=14y+ax=\tfrac14 y+a and y=14x+by=\tfrac14 x+b intersect at the point (1,2).(1,2). What is a+b?a+b?

00

34\dfrac{3}{4}

11

22

94\dfrac{9}{4}

Solution:

Substituting (1,2)(1,2): from 1=14(2)+a1=\tfrac14(2)+a we get a=12,a=\tfrac12, and from 2=14(1)+b2=\tfrac14(1)+b we get b=74.b=\tfrac74.

Then a+b=12+74=94.a+b=\tfrac12+\tfrac74=\tfrac94.

Thus, the correct answer is E.

Problem 12 in Other Years