Mathematics · Grades 10–12
Permutations
Use permutations when order matters and no item is repeated.
The key idea
Use permutations when order matters and no item is repeated.
P(n,r) = n!/(n − r)!
Worked examples
How many ordered selections of 5 distinct items can be made from 9 items without repetition?
9!/4! = 15120
15120
How many ordered selections of 3 distinct items can be made from 8 items without repetition?
8!/5! = 336
336
Try it yourself
How many ordered selections of 2 distinct items can be made from 11 items without repetition?
How many ordered selections of 2 distinct items can be made from 13 items without repetition?
Check your understanding
Answers and marking notes
- 110
11!/9! = 110
- 156
13!/11! = 156
Further reading and review references
These are reference links, not copied exercises, institutional endorsement or proof of independent review.
Learning preview · teacher review required. Grade bands are approximate, not official curriculum alignment.