Answer
a. 0.632
b. 0.140
c. 0.0031
d. 0.624
Work Step by Step
a. P(not medium and not medium) = $\frac{16}{20} * \frac{15}{19}$ = 0.632
b. P(first medium is third) = $\frac{16}{20} * \frac{15}{19} * \frac{4}{18}$ = 0.140
c. P(extra large and extra large and extra large and extra large) =
$\frac{6}{20} * \frac{5}{19} * \frac{4}{18} * \frac{3}{17}$ = 0.0031
d. P(at least one medium in four) =
1 - P(not medium and not medium and not medium and not medium) =
1 - ($\frac{16}{20} * \frac{15}{19} * \frac{14}{18} * \frac{13}{17}$) =
1 - 0.376
= 0.624
