Question

A 3-digit numeral is formed by selecting digits at random from 2,4,6,7 without repetition. Find the probability that the number formed contains only even digits. P(even digits)

Answer 1

3/4.

Explanation:

Total number of ways to pick 3 digits from the 4 given digits = 4P3

= 4!/ 1! = 24 ways.

The odd numbers are formed when 7 is the last digit of the 3 digits and this will be in 6 numbers 247, 267, 427, 467, 647 and 627 . So there will be 24 - 6 = 18 even numbers.

So the probability of only even digits = 18/24 = 3/4.