13. The area of the intersection of a triangle and a circle is $45 \%$ of the total area of the diagram. The area of the triangle outside the circle is $40 \%$ of the total area of the diagram. What percentage of the circle lies outside the triangle?
A $20 \%$
B $25 \%$
C $30 \%$
D $33 \frac{1}{3} \%$
E $35 \%$
SolUtion
B

The area of the circle inside the triangle is $45 \%$ of the total area of the diagram. The area of the circle outside the triangle is $(100-40-45) \%=15 \%$ of the total area of the diagram. Therefore, the percentage of the circle that lies outside the triangle is $\frac{15}{15+45} \times 100=25 \%$.