順列・組合せの計算機
n（選ぶもとの個数）と r（選ぶ個数）を入力してください。
結果
値を入力して「計算」を押すと結果が表示されます。
公式
Permutations: order matters.
Combinations: order does not matter.
この計算ツールの使い方
- Enter whole numbers with r no bigger than n.
- Press Calculate to get both counts.
解き方付き例題
Choose 2 from 5
5P2 = 5 × 4 = 20 ordered arrangements.
5C2 = 20 / 2! = 10 unordered selections.
よくある質問
When does order matter?
For rankings or codes (permutations). For teams or hands of cards, order doesn’t matter (combinations).
Are the answers exact?
Yes — even very large counts are computed exactly.