2 Choose 1

Combination Calculator
Total items (n)
Items chosen (k)

What is 2 choose 1?

Answer

2 choose 1 is
2

Order doesn't matter, no repeats: 2 ways to choose 1 of 2 items.

C(2, 1) = 2! / (1! · 1!)

= 2 / 1

= 2

Row 2 of Pascal's triangle
k2 choose k
01
12
21

Row sum: 22 = 4 — all subsets of 2 items.

See Also

Recalculate with different values ↑

n choose 1 for other n

n choose 1Answer
1 choose 11
2 choose 12
3 choose 13
4 choose 14
5 choose 15
6 choose 16
7 choose 17
8 choose 18
9 choose 19
10 choose 110
11 choose 111
12 choose 112
13 choose 113
14 choose 114
15 choose 115

FAQ

What is 2 choose 1?

2 choose 1 is 2

Why is 2 choose 1 the largest number in row 2?

In row 2 of Pascal's triangle the numbers grow towards the middle and shrink after it, because n choose k = n choose (n − k). With an even n the middle is k = 1, so 2 choose 1 = 2 is the largest: 2 choose 0 is only 1.

How many ways are there if order matters?

The same 2: with 1 chosen item there is only one order, so P(2, 1) = 2 choose 1 = 2. Order starts to matter from 2 items on: n × (n − 1) arrangements.

See Also