2010 AMC 10B Problem 4

Below is the professionally curated solution for Problem 4 of the 2010 AMC 10B, from LIVE by Po-Shen Loh. You can also try the full timed exam, view all 2010 AMC 10B solutions, or check the answer key.

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Concepts:custom operationmean

Difficulty rating: 870

4.

For a real number x,x, define (x)\heartsuit(x) to be the average of xx and x2.x^2. What is (1)+(2)+(3)?\heartsuit(1)+\heartsuit(2)+\heartsuit(3)?

33

66

1010

1212

2020

Solution:

We have (1)=1+122=1, \heartsuit(1) = \dfrac{1 + 1^2}{2} = 1, (2)=2+222=3, \heartsuit(2) = \dfrac{2 + 2^2}{2} = 3, and (3)=3+322=6. \heartsuit(3) = \dfrac{3 + 3^2}{2} = 6.

Then 1+3+6=10. 1 + 3 + 6 = 10.

Thus, C is the correct answer.

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