In mathematics, permutation is known as the process of arranging a set in which all the members of a set are arranged into some series or order. The process of permuting is known as the rearranging of its components if the set is already arranged. Permutations take place, in more or less important ways, in almost every area of mathematics. They frequently appear when different commands on certain finite sets are considered.
What is a Combination?
A combination is an act of choosing items from a group, such that (not like permutation) the order of choice does not matter. In smaller cases, it is possible to count the number of combinations. Combination refers to the union of n things taken k at a time without repetition In combination you can select the items in any order. To those combinations in which re-occurrence is allowed, the terms k-selection or k-combination with replication are frequently used.
Permutation Formula
In permutation r things are selected from a set of n things without any replacement. In this order of selection matter.
nPr = (n!) / (n-r)!
Here,
n = set size, the total number of items in the set
r = subset size , the number of items to be selected from the set
Combination Formula
In combination r things are selected from a set of n things and where the order of selection does not matter.
nCr = n!/(n−r)!r!
Here,
n = Number of items in set
r = Number of items selected from the set
From a standard 52-card deck, how many 5-card hands consist entirely of red cards?
Solution:
There are total 26 red card i.e., 13 hearts and 13 diamonds.
From 26 red cards, choose 5.
The answer is the binomial coefficient
(26C5) and you can read this as 26 choose 5.
So there are
(26C5) = 26! ⁄ 5!(26−5)!
= 26! ⁄ 5!21!
= 26×25×24×23×22×21! ⁄ 5×4×3×2×1×21!
= 26×25×24×23×22 ⁄ 5×4×3×2
= 26⁄2×25⁄5×24⁄12×23×22
= 13×5×2×23×22
= 13×10×23×22
= 130×506 = 65,780
Possible 5-card hands consisting of only red cards.
Similar Questions
Question 1: From a standard 52 card deck, how many 6 card hands consist entirely of black cards?
Solution:
There are total 26 black cards i.e., 13 clubs and 13 spades.
From 26 black cards, choose 6.
The answer is the binomial coefficient
(26C6) and you can read this as 26 choose 6.
So there are
(26C6) = 26! ⁄ 6!(26−6)!
= 26! ⁄ 6!20!
= 26×25×24×23×22×21×20! ⁄ 6×5×4×3×2×1×20!
= 26×25×24×23×22×21 ⁄ 6×5×4×3×2
= 26⁄2×25⁄5×24⁄24×23×22×21⁄3
= 13×5×23×22×7=13×115×154
= 1495×154 = 230,230
Possible 6-card hands consisting of only black cards.
Question 2: From a standard 52-card deck, how many 2-card hands consist entirely of black cards?
Solution:
There are total 26 black cards i.e., 13 clubs and 13 spades.
From 26 black cards, choose 2.
The answer is the binomial coefficient
26C2 and you can read this as 26 choose 2.
So there are
26C2 = 26! ⁄ 2!(26−2)!
= 26! ⁄ 2!24!
= 26×25×24! ⁄ 2×1×24!
= 26×25 ⁄ 2
= 26⁄2×25
= 13×25=13×25
= 325
Possible 2-card hands consisting of only black cards.
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Last Updated :
21 Nov, 2021
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