20 Choose 5
Combination Calculator
What is 20 choose 5?
Answer
20 choose 5 is
15,504
Order doesn't matter, no repeats: 15,504 ways to choose 5 of 20 items.
C(20, 5) = 20! / (5! · 15!)
= (20 × 19 × 18 × 17 × 16) / (5 × 4 × 3 × 2 × 1)
= 1,860,480 / 120
= 15,504
If order matters (permutations): P(20, 5) = 20 × 19 × 18 × 17 × 16 = 1,860,480 — each combination in 5! = 120 orders.
| k | 20 choose k |
|---|---|
| 0 | 1 |
| 1 | 20 |
| 2 | 190 |
| 3 | 1,140 |
| 4 | 4,845 |
| 5 | 15,504 |
| 6 | 38,760 |
| 7 | 77,520 |
| 8 | 125,970 |
| 9 | 167,960 |
| 10 | 184,756 |
| 11 | 167,960 |
| 12 | 125,970 |
| 13 | 77,520 |
| 14 | 38,760 |
| 15 | 15,504 |
| 16 | 4,845 |
| 17 | 1,140 |
| 18 | 190 |
| 19 | 20 |
| 20 | 1 |
Row sum: 220 = 1,048,576 — all subsets of 20 items.
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See Also
- Random Number Generator - Pick a random whole number between two bounds
- Percent to Probability Converter - Convert Percents to "1 in X" Probability Chance
- Factors of a Number - List all Factors and Factor Pairs of a Number
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