anon1 wrote:

Each of the balls in a jar is either red, green or blue. If one ball is removed at random, what is the probability that the ball will be green?

(1) There are 7 blue balls in the jar.

(2) The probability that the ball will be red is 1/4

I thought this was C because I thought having number of blue balls would close the unknown down to exact numbers. Where am I mistaken? Is there a way to think through this in an elegant manner?

The easiest way to think through is always the most basic way. For knowing probability of anything we need to know favourable and total outcomes, in this case number of green balls and total balls. Or probability of it not happening ie not favorable/total in this case number of red+blue and total balls.

In the given question

Statement 1 doesnt help to get total or green ball or red+blue. Insufficient

Statement 2 gives only red/total. Insufficient

Combining these two we still can not find red+blue/total or green/total.

Therefore Ans E it is.

_________________

Lets Kudos!!!

Black Friday Debrief