GMAT Prep - Probability (Tough Problem)

[rosh26]

Please explain. Thanks.

[ashishjha100]

IMO A

since there are 25 balls in box , we dont know hw many white or hw many even numbered.

st1: tells that no even numbered white balls are there in the box. Nw its clear that 10 red, 10 blue and 5 white odd numbered balls in the box.

So probability of picking a white ball = 5/25 =1/5
So probability of picking a even no: ball = 10/25

so total probability = 1/5+10/25

st2: let there be w white balls and n even no: balls

(w/25) - (n/25) = 2/10

only w - n is obtained......so insufficient

[parallel_chase]

I think the answer should be E.

Statement I

Probability of white ball X even ball is 0

Either there are no even no. balls or there are no white balls. This simply means that there no white balls with even numbers.

Insufficient.

Statement II

Probability of White ball - even ball = 1/5

We dont know anything about white balls or even balls. Insufficient.

Combining I & II

Probability of white ball X even ball = 0
Probability of White ball - even ball = 1/5
Probability white ball + even ball =?

We still dont know how many whites and how many are even.
Therefore, Insufficient.

Hence E is the answer.

Whats the OA?

[rosh26]

OA is E