Probability:

Probability means possibility. It is a branch of mathematics that deals with the occurrence of a random event.

The value is expressed between zero and one. Probability has been introduced in Maths to predict how likely events are to happen.

Combination:

nCr = n! / ( r! * (n-r)!)

nCr is used to know number of ways to choose r objects from n number of objects.

Ex:  I have 3 balls b1,b2,b3 and I want to choose 2 out of them so how will i choose?

I can either choose b1,b2 or b2,b3 or b3,b1. so that means i have 3 ways to choose. this same thing can be done using nCr here n=3 i.e toatal no of objects and r=2 i.e no of objects i need to to choose so putting values of n and r in formulae 3C2 =3!/(3–2)!.2!.=3

Probability formulas:

P(E)= n(E)/n(S)

Where n(S) = total outcome

And     n(E) = favorable outcome

Know About Factorials:

n! = n * (n-1) * (n-2) * (n-3) ………..* 1

5! = 5 x 4 x 3 x 2 x 1 =120

Below factorials need to keep in mind:

0! = 1      1! = 1      2!= 2      3! = 6         4! = 24

5! =120.    6! =720        7!=5040          8! =40320

When two coins are tossed, then find the probability of getting two heads.

a) 1 / 3                          b) 1 / 4                          c) 1 / 2                          d) 3 / 4

Solution:

When two coins are tossed, total no. of possible outcomes n(S) = 2² = 4

n(S) = {HH, HT, TH, TT}

No. of favourable events of getting 2 heads, n(E) = {HH} = 1

⸫ Required probability P(E) = n(E) / n(S) = 1 / 4.

Answer: b

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