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Problem 279: (2012 AMC 12b, 20)
A trapezoid has side lengths $3$, $5$, $7$, and $11$. The sums of all the possible areas of the trapezoid can be written in the form of $r_1\sqrt{n_1}+r_2\sqrt{n_2}+r_3$, where $r_1$, $r_2$, and $r_3$ are rational numbers and $n_1$ and $n_2$ are positive integers not divisible by the square of any prime. What is the greatest integer less than or equal to $r_1+r_2+r_3+n_1+n_2$? $\textbf{(A)}\ 57\qquad$ $\textbf{(B)}\ 59\qquad$ $\textbf{(C)}\ 61\qquad$ $\textbf{(D)}\ 63\qquad$ $\textbf{(E)}\ 65$
Solution
Exercise 279: Solution
A trapezoid has side lengths $2$, $4$, $6$, and $10$. The sum of all its possible areas can be written as $r_1\sqrt{n_1}+r_2\sqrt{n_2}+r_3$, where $r_1,r_2,r_3$ are rational and $n_1,n_2$ are squarefree positive integers. What is the greatest integer less than or equal to $r_1+r_2+r_3+n_1+n_2$?
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