PROBABILITY C4

A number is chosen at random from 1 – 9 inclusive. Find the probability that it is a multiple of five or an even number.

Solution

THIS IS A MUTUALLY EXCLUSIVE EVENT.

Let n(S) represent sample space

P(E) = probability of even number

P(M) = probability of a multiple of 5

n(S) = {1, 2, 3, 4, 5, 6, 7, 8, 9,} = 9

n(E) = {2, 4, 6, 8, 10} = 5

n(M) = {5} = 1

P(E) = ⁵/9

P(M) = ¹/9

………………………….

P(EuM) = P(E) + P(M)

P(EuM) = ⁵/9 + ¹/9

∴ P(EuM) = ⁶/9 = ²/3

TRY THIS………………

A number is chosen at random from 7 – 14 inclusive. Find the probability that it is a prime or an even number.