7. Probability
7.15 Mixed combinations and permutations
Interactive practice questions
If you can choose one item from a group of $a$a items and a second item from a group of $b$b items, what is the total number of two-item choices?
Easy
1min
The number of possible permutations of $r$r objects taken from $n$n items is $\nPr{n}{r}$nPr. Express this in factorial form.
Easy
1min
The number of possible combinations of $r$r objects taken from $n$n items is $\nCr{n}{r}$nCr. Express this in factorial form.
Easy
< 1min
Evaluate $\frac{\nPr{8}{3}}{3!}-\nCr{8}{3}$8P33!−8C3.
Easy
1min
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