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2010 AMC 10B Problems/Problem 4

Revision as of 13:38, 30 May 2010 by Fermat007 (talk | contribs) (Created page with 'The average of two numbers, <math>a</math> and <math>b</math>, is defined as <math>\frac{a+b}{2}</math>. Thus the average of <math>x</math> and <math>x^2</math> would be <math>\f…')
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The average of two numbers, $a$ and $b$, is defined as $\frac{a+b}{2}$. Thus the average of $x$ and $x^2$ would be $\frac{x(x+1)}{2}$. With that said, we need to find the sum when we plug, $1$, $2$ and $3$ into that equation. So:


$\frac{1(1+1)}{2} + \frac{2(2+1)}{2} + \frac{3(3+1)}{2} = \frac{2}{2} + \frac{6}{2} + \frac{12}{2} = 1+3+6= \boxed{\mathrm{(C)} \text{ or } 10}$.

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