How to calculate permutations and combinations (nPr and nCr)
nCr counts the ways to choose r items from n when order doesn’t matter. nPr counts them when order does. Here’s how many ways there are to choose 4 items from 10.
Combinations with nCr
- Type 1 0.
- Tap nCr.
- Type 4 and tap =. The answer is 210.
Permutations with nPr
For arrangements, where order matters, use SHIFT nPr, the second function of nCr. 10 nPr 4 is 5040: the number of ways to fill first, second, third and fourth place from 10 people.
Factorials with x!
x! gives the factorial. 5! is 120, and (5 + 3)! is 40 320.
Limits
n and r must be whole numbers, with r no bigger than n. Factorials work for whole numbers from 0 to 69.
For fractions of these counts, such as probabilities, see how to calculate fractions.
