A combination calculator is a tool that helps you determine the number of possible combinations when selecting a certain number of items from a larger set of items, without regard to the order in which the items are selected.

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## What is Combination Calculator

A combination calculator is a tool used to calculate the number of possible combinations of a set of items. A combination is a selection of items from a set where the order of selection does not matter. For example, selecting three balls from a set of five balls without regard to their order would be a combination.

The formula for calculating the number of combinations of n items taken r at a time is:

C(n, r) = n! / (r! * (n-r)!)

where n is the total number of items, r is the number of items selected, and “!” represents the factorial function.

A combination calculator simplifies the process of calculating combinations by allowing you to input values for n and r and then computing the result. Some calculators may also provide a visual representation of the items selected, such as a table or list.

For example, if you have a set of 6 items and you want to know how many combinations of 3 items are possible, you can use the combination calculator and enter n = 6 and r = 3. The calculator will then use the formula above to calculate that there are 20 possible combinations of 3 items from a set of 6.

## Difference between Combinations and Permutations?

The main difference between combinations and permutations is that in permutations, the order of the items matters, while in combinations, the order does not matter.

Permutations refer to the number of arrangements of a set of items in a specific order. For example, if you have 3 letters A, B, and C, the number of permutations of these letters taken 2 at a time would be 6, since there are 6 possible arrangements: AB, AC, BA, BC, CA, and CB.

Combinations, on the other hand, refer to the number of ways to choose a subset of items from a larger set, without regard to the order in which they are chosen. For example, if you have 3 letters A, B, and C, the number of combinations of these letters taken 2 at a time would be 3, since there are 3 possible combinations: AB, AC, and BC.

Another way to differentiate between permutations and combinations is by their formulas. The formula for permutations is:

nPr = n! / (n – r)!

where n is the total number of items and r is the number of items to be selected.

The formula for combinations is:

nCr = n! / (r! * (n – r)!)

where n is the total number of items and r is the number of items to be selected.

In summary, permutations involve arrangements of items in a specific order, while combinations involve choosing a subset of items without regard to their order.

## nCr formula

The formula for nCr, the number of combinations of n items taken r at a time, is:

nCr = n! / (r! * (n – r)!)

where n is the total number of items and r is the number of items to be selected. The exclamation mark “!” represents the factorial function.

The formula can be read as follows: first, find the factorial of n, which is the product of all positive integers up to n (i.e., n! = n * (n-1) * (n-2) * … * 3 * 2 * 1). Then, divide this by the product of the factorials of r and n-r (i.e., r! * (n-r)!).

For example, if you want to find the number of combinations of 5 items taken 2 at a time, you can use the formula:

nCr = 5! / (2! * (5-2)!) = 10