Question

In the figure above, if the area of triangle CAF is equal to the area of rectangle CDEF, what is the length of segment AD?

• A. $\frac{7}{2}$
• B. 5
• C. 7
• D. $\frac{15}{2}$
• E. 15

Answer 1

The correct option is C 7

Area of rectangle $DCFE$ is $15\times 7=105$, which is equal to the area of triangle $ACF$.

Area of triangle $ACF$ is $\frac{1}{2}\times 15\times (7+AD)$

$\therefore$ $\frac{1}{2}\times 15\times (7+AD)=105$

$\therefore AD=7$