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    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.

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    https://calculat.io/en/number/combinations/2--1Copy
    <a href="https://calculat.io/en/number/combinations/2--1">2 Choose 1: Combinations C(2, 1) - Calculatio</a>Copy
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    2 Choose 1: Combinations C(2, 1). 2 choose 1 = 2: the number of ways to choose 1 of 2 items when order doesn't matter and nothing repeats. C(2, 1) = 2 / 1.
    https://calculat.io/en/number/combinations/2--1/generated.jpgCopy

    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
    Recalculate with different values ↑

    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