4. What fraction of this diagram is shaded?
A $\frac{13}{32}$
B $\frac{1}{2}$
C $\frac{9}{16}$
D $\frac{5}{8}$
E $\frac{13}{16}$
4. D We choose units so the outer square has side-length 4 , and hence area 16 .
The unshaded area of the square consists of two congruent triangles of base 3 and height 2 .
So the area of each unshaded triangle is $\frac{1}{2} \times 3 \times 2=3$.
Hence the area of the shaded part of the square is $16-2 \times 3=10$.
Therefore the fraction of the square which is shaded is $\frac{10}{16}=\frac{5}{8}$.