Question

A number is selected at random from the first 1000 natural numbers. What is the probability that it would be a multiple of 5 or 9​

Answer 1

Answer:

Step-by-step explanation:

First 1000 natural no belong the following set {1,2,3,…,1000} with cardinality = 1000

Multiples of 7 less than 1000 = Quotient of (1000/7) = 142

Multiples of 11 less than 1000 = Quotient of (1000/11) = 90

As 7 & 11 are both primes so multiples of 7*11 = 77 will be included in both multiples of 7 and multiples of 11

Multiples of 77 less than 1000 = Quotient of (1000/77) = 12

Hence, all natural numbers below 1000 which are either multiples of 7 or of 11 = 142+90–12 = 220

So, Prob(this event) = 220/1000 = 0.22

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