Question

(ntse exam question) A number is selected at random from fi33/4

rst 50 natural numbers. The probability that selected number is a multiple of 3 or 4 is:

Answer 1

Q: A number is selected at random from first 50 natural numbers. The probability that selected number is a multiple of 3 or 4 is:

A:
number of multiples of 3 below 50 = 50/3 = 16 (ignore the remainder)

number of multiples of 4 below 50 = 50/4 = 12 (ignore the remainder)

Common multiples of 3 and 4 = multiples of 12

number of multiples of 12 below 50 = 50/12 = 4
(these are the ones we have counted both for 3 and 4, so it needs to be subtracted once)

So total multiples of 3 or 4 below 50 = 16+12 -4 = 24

Probability = 24/50 = 12/25