Question

A number is chosen at random from 1 to 25 inclusive. Find the probability of selecting an odd number or a multiple of 5.

Answer 1

Tootal possible outcomes = 25

Total odd numbers present in 1 to 25 are = 13 {1,3,5,7,9,11,13,15,17,19,21,23,25}

P(odd numbers) = P(A) = 13 / 25 = 0.52

Multiple of 5 present in 1 to 25 are = P(B) = 5 {5,10,15,20,25}

P(multiple of 5) = 5/25 = 0.2

P(probability of selecting an odd number or a multiple of 5.) = P(A U B)

where,

A = {1,3,5,7,9,11,13,15,17,19,21,23,25}

B = {5,10,15,20,25}

A n B = { 5 , 15 , 25}

P(A n B) = 3/25 = 0.12

Threfore required probability is,

P(A U B) = P(A) + P(B) - P(A n B) = 0.52 + 0.2 - 0.12 = 0.6

P(probability of selecting an odd number or a multiple of 5) = 0.6

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