Table of Contents

## What is the number of ways of selecting from a set when the order is not important?

When selecting more than one item without replacement and order is important, it is called a Permutation. When order is not important, it is called a Combination. Example 2: There are 10 entries in a contest.

**What do you call the number of ways of selecting from a set?**

permutations and combinations, the various ways in which objects from a set may be selected, generally without replacement, to form subsets. This selection of subsets is called a permutation when the order of selection is a factor, a combination when order is not a factor.

**What do you call to the selection of objects regardless of their order?**

We sometimes make a selection from a set without regard to order. Such a selection is called a combination.

### How do you find the number of combinations when order matters?

In our example the order of the digits were important, if the order didn’t matter we would have what is the definition of a combination. The number of combinations of n objects taken r at a time is determined by the following formula: C(n,r)=n! (n−r)!

**Is it permutation or combination?**

A permutation is an act of arranging the objects or numbers in order. Combinations are the way of selecting the objects or numbers from a group of objects or collection, in such a way that the order of the objects does not matter.

**What is the term used to refer to the selection made from a set without regard to their order?**

A combination is a selection of all or part of a set of objects, without regard to the order in which they were selected.

## What is the selection of objects from a set?

A combination is a selection of objects from a set of objects, that is objects are chosen from a particular set and listed, but the order in which the objects are listed is immaterial. Therfore, The number of permutations of n distinct objects taken k at a time can be written as: P k = n! / (n – k) !

**How do you choose between permutation and combination?**

The difference between combinations and permutations is ordering. With permutations we care about the order of the elements, whereas with combinations we don’t. For example, say your locker “combo” is 5432. If you enter 4325 into your locker it won’t open because it is a different ordering (aka permutation).

**Are the number of different ways in which objects can be arranged in order?**

These letters can be arranged a number of different ways (XYZ, XZY, YXZ, etc.) Each of these arrangements is a permutation. A permutation is an arrangement of all or part of a set of objects, with regard to the order of the arrangement. This means that XYZ is considered a different permutation than ZYX.

### What is 20P2?

20P2=20! 18!=( 20×19)=380.

**What is 10P4?**

There are 10 digits (0, 1, …, 9) and each one appears at most once. The number of orderings of these digits is 10P4 = 5040.