South African Mathematics Olympiad

When $a$ is increased by $20\%$ and $b$ is decreased by $20\%$ the resulting values are equal. The ratio of $a$ to $b$ is

(A) $\frac{1}{2}$ (B) $1$ (C) $\frac{2}{3}$ (D) $\frac{3}{4}$ (E) $\frac{4}{3}$