2015-II-09

答案：B
設 $\$x$ 為該紀念品的售價。則新的售價

$\begin{array}{cl}
= & x \times (1+70\%) \times (1-60\%) \\
= & \$ 0.68x
\end{array}$

所以，該紀念品的售價的百分變化

$\begin{array}{cl}
= & \dfrac{0.68x – x}{x} \times 100\% \\
= & \dfrac{-0.32x}{x} \times 100\% \\
= & -0.32 \times 100\% \\
= & -32\%
\end{array}$