Question

A person chooses 2 different odd numbers at a time in a set containing the numbers from 3 to 9. If event E is that 7 is chosen 1st, then find the set representing E.

Answer 1

The event E is picking 7 first regardless of the second pick. Furthermore, the very first condition is that 2 odd numbers are picked. So, we need the probability of picking 7 first and then an odd number as the second pick.

The only options that fulfill both conditions are: (7,3), (7,5), (7,7), (7,9).

The answer is then

`E=\lbrace(7,3),(7,5),(7,7),(7,9)\rbrace`

Where (a,b) represents picking a first and b second.