答案：(a) (i) $\dfrac{3}{5}$ (ii) $\dfrac{3}{20}$ (iii) $\dfrac{13}{20}$ (iv) $\dfrac{1}{4}$ (b) (i) $\dfrac{3}{79}$ (ii) 否
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- 所求的概率
$\begin{array}{cl}
= & \dfrac{48}{80} \\
= & \dfrac{3}{5}
\end{array}$ - 所求的概率
$\begin{array}{cl}
= & \dfrac{12}{80} \\
= & \dfrac{3}{20}
\end{array}$ - 所求的概率
$\begin{array}{cl}
= & \dfrac{3}{5} + \dfrac{16}{80} – \dfrac{3}{20} \\
= & \dfrac{13}{20}
\end{array}$ - 所求的概率
$\begin{array}{cl}
= & \dfrac{\frac{3}{20}}{\frac{3}{5}} \\
= & \dfrac{1}{4}
\end{array}$
- 所求的概率
-
- 所求的概率
$\begin{array}{cl}
= & \dfrac{16}{80} \times \dfrac{15}{79} \\
= & \dfrac{3}{79}
\end{array}$ - 選出兩名學生穿著相同尺碼襯衣的概率
$\begin{array}{cl}
= & \dfrac{28}{80} \times \dfrac{27}{79} + \dfrac{36}{80} \times \dfrac{35}{79} + \dfrac{3}{79} \\
= & \dfrac{141}{395} \\
< & \dfrac{1}{2} \end{array}$所以，選出的兩名學生穿著相同尺碼襯衣的概率並不大於穿著不同尺碼襯衣的概率。
- 所求的概率
