Friday, 7 July 2017

PROBABILITY 2


A number is chosen at random from 21 – 30 inclusive. Find the probability that it is a prime or a multiple of  4.

Solution

THIS IS A MUTUALLY EXCLUSIVE EVENT!

Let n(S) represent sample space
P(M) = probability of a multiple of  4
P(R) = probability of prime number

n(S) = {21, 22, 23, 24, 25, 26, 27, 28, 29, 30} = 10
n(M) = {24, 28} = 2
n(R) = {23, 29} = 2
P(M) = 2/10
P(R) = 2/10
………………………….
P(MuR) = P(M) + P(R)

P(MuR) = 2/10 + 2/10

P(MuR) = 4/10

              = 2/5


P(MuR) = 2/5 answer

TRY THIS…………………


A number is chosen at random from 10 – 30 inclusive. Find the probability that it is a prime or a multiple of 5. 


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