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1 Choose 2

Combination Calculator

What is 1 choose 2?

Answer

1 choose 2 is

0

Order doesn't matter, no repeats: you can't choose 2 items from 1, so there are 0 ways.

2 > 1 → C(1, 2) = 0

If order matters (permutations): P(1, 2) = 0 too.

Row 1 of Pascal's triangle
k	1 choose k
0	1
1	1

Row sum: 2¹ = 2 — all subsets of 1 item.

k = 2 is past the end of row 1.

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https://calculat.io/en/number/combinations/1--2

<a href="https://calculat.io/en/number/combinations/1--2">1 Choose 2: Combinations C(1, 2) - Calculatio</a>

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1 Choose 2: Combinations C(1, 2). 1 choose 2 = 0: you can't choose 2 of 1 item without repeats, so there are 0 ways when order doesn't matter.

https://calculat.io/en/number/combinations/1--2/generated.jpg

n choose 2 for other n

n choose 2	Answer
1 choose 2	0
2 choose 2	1
3 choose 2	3
4 choose 2	6
5 choose 2	10
6 choose 2	15
7 choose 2	21
8 choose 2	28
9 choose 2	36
10 choose 2	45
11 choose 2	55
12 choose 2	66
13 choose 2	78
14 choose 2	91
15 choose 2	105

Recalculate with different values ↑

FAQ

What is 1 choose 2?

1 choose 2 is 0

Why is 1 choose 2 zero?

You can't pick 2 different items when there are only 1, so there are no ways at all and the answer is 0, not an error. Often the numbers are swapped: 2 choose 1 = 2.

How many ways are there if order matters?

Still none: 2 different items can't be taken from 1 in any order, so P(1, 2) = 0 too.

See Also