1959 AHSME Problems/Problem 40

Problem

In $\triangle ABC$ , $BD$ is a median. $CF$ intersects $BD$ at $E$ so that $\overline{BE}=\overline{ED}$ . Point $F$ is on $AB$ . Then, if $\overline{BF}=5$ , $\overline{BA}$ equals: $\textbf{(A)}\ 10 \qquad\textbf{(B)}\ 12\qquad\textbf{(C)}\ 15\qquad\textbf{(D)}\ 20\qquad\textbf{(E)}\ \text{none of these}$

Solution

Make a line DG which is parallel to FC. We know that GF = BF = 5, since BFE is similar to BGD.

Since ADG is similar to ACB, we know that AG is 10.

Thus, AF = 10 + 5 = 15, which is answer $\fbox{\textbf{(C)}}$ .

1959 AHSC (Problems • Answer Key • Resources)
Preceded by Problem 39	Followed by Problem 41
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1959 AHSME Problems/Problem 40

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