A complete guide to Permutation, Combination and Probability. All you need for GMAT

[mally]

I'm sorry-that means somethings wrong on my comp!

[mally]

Got it on this one.

[mally]

Hi,
Thanks for your answers , I'm solving the exercise and comparing my answers with yours.How did you do No.4-can u show me? your answer is D isn't it? I don't know why B is marked already.

A bag of 10 marbles contains 3 red marbles and 7 blue marbles. If two marbles are selected at random, what is the probability that at least one marble is blue?



A. 21/50

B. 3/13

C. 47/50

D. 14/15

E. 1/5

Thanks!

[TwinnSplitter]

probability that they're both red = (3/10) x (2/9) = 1/15

Probability that at least one is blue = 1 - probability that they're both red
= 1 - 1/15

= 14/15

So the answer is D

[TwinnSplitter]

were the rest of your answers the same as mine?

[mally]

My answer for the 9th problem is D not E.How did u arrive at 1/32?
Problem given below:

If four fair coins are tossed, what is the probability of all four coming up heads?



A. 1/4

B. 1/6

C. 1/8

D. 1/16

E. 1/32

[mally]

nope.look at the next one i've posted about 4 coins. But I'll post all my answers -still going through it.whew!

[TwinnSplitter]

I also put D (not E) for that question. You were probably looking at the two E's that I put for the two questions before that. So I got 1/16 too

[Nity]

Thanks for the Probability document and the link. They've been really helpful

[prometheus]

Do we have the OAs ?
My answers:
B,C ,A,C, D,B,B,E,E,D,B,D,E,D,B,E,A,D,D,D

Twinsplitter:
My answers were the same as yours except for the 6th question from the end.

A fair, six-sided die is rolled. What is the probability of obtaining a 3 or an odd number?

My answer to this was 1/6 + 1/2 = 2/3 and option (D). Is this right ?