Problem Solving

If a man tosses a coin until he obtains either 3 heads or 3 tails, what is the probability he will need 5 tosses?

(a) 1/4
(b) 3/8
(c) 5/8
(d) 7/16
(e) 11/32

the man will need 5 tosses when he has 2 heads or two tails in the first 4 tosses. probability of 2 heads/2 tails in the 4 tosses: 4C2/2^4
=6/16=3/8
hence, B

(took a cue from your solution of the probability question on baseball match )

scoobydooby wrote:the man will need 5 tosses when he has 2 heads or two tails in the first 4 tosses. probability of 2 heads/2 tails in the 4 tosses: 4C2/2^4
=6/16=3/8
hence, B

(took a cue from your solution of the probability question on baseball match )

You get it buddy. Several of these problems are related. I mean there is only so much spin you can put on a probability or a triangle question. This forum is beautiful.

thanks for posting them dtweah, whats the source? the questions are thought provoking

scoobydooby wrote:thanks for posting them dtweah, whats the source? the questions are thought provoking

I am getting them from David Essner and University of Maryland high school Math competitions. I just discovered that their questions approximate the difficulty level of GMAT especially for David Essner, (Just Google these) Some of Maryland's may be too stronger but the questions put you in gear for the tough GMAT Stuff. Anybody who practices these questions spanning several years will be in more than in good shape for the GMAT or GRE.