maths….?

meg: maths….?
how do we get the answer for 5P3 and 5C2 without using the calculator?

Answers and Views:

Answer by CogitoErgoCogitoSum
Permutations and Combinations, in terms of those particular functions, are determined using factorials.

aPb = a! / (b-a)!
aCb = aPb / b!

Do you know what a factorial is? any number with an exclamation point, in mathematics, is being factorial”-ed”.

a! = 1 × 2 × 3 × 4 … × (n-1) × n

All numbers from 1 to the number are being multiplied together.

So then…
to find 5P3 we would have to find the factorials of five and of two (5-3).
5! = 1 × 2 × 3 × 4 × 5 = 120
2! = 1 × 2 = 2

so 5! / 2! = 60… which is 5P3

now… to find 5C3 we take 5P3 and divide by 3!

3! = 1 × 2 × 3 = 6

so, 5C3 = 5P3 / 6 = 60 / 6 = 10

Answer by scooby
How about you pick up a book and find out?

Answer by sarkartapas2005
Each of the different arrangements,which can be made of a given number of things by taking some or all of them at a time is called Permutation.
5P3 may be calculated as 5*4*3=60
Each of the groups or selections that can be made by taking at a time some or all of things (without regard to the order of the things in each group)is called a combination
5C2 may be calculated as 5!/(5-2)!2! (the sign ! stands for permutaion)
=5!/3!2!
=60/3*2*2
=5