5) If we increase the length of the base of a rectangle by $30 \%$ and that of the height by $50 \%$, the area increases by
(A) $195 \%$
(B) $115 \%$
(C) $150 \%$
(D) $95 \%$
(E) $80 \%$.
5) The answer is (D)

Let's call $b$ the base of the rectangle and $h$ its height. By increasing the base and height by 30% and 50% respectively, the area will become

$$
\left(1+\frac{30}{100}\right) b \times\left(1+\frac{50}{100}\right) h=\left(1+\frac{30}{100}+\frac{50}{100}+\frac{1500}{10000}\right) b h=\left(1+\frac{95}{100}\right) b h .
$$

Therefore, the area will increase by 95%.