BREAKING: Target Test Prep releases Brand New 2026 On Demand GMAT prep course

Redeem

Coin Probability

Expert replies
Source: — Problem Solving |

by mathbyvemuri » Mon May 07, 2012 1:07 am
It's a formula based problem.
"The probability of getting exactly k results out of n flips is: nCk/2^n"
6C3/2^6 = 20/2^6 = 5/2^4
Answer option "E"
Join the discussion

by Bill@VeritasPrep » Mon May 07, 2012 7:29 am
If we're looking for exactly 3 heads (and therefore exactly 3 tails), we can use our permutation with repeating elements formula: 6!/(3!3!) = 20. For any binomial event, the total number of possibilities is equal to 2^n where n is the number of events. 2^6=64, so the probability of exactly 3 heads is 20/64, or 5/16, which is 5/2^4.
Join Veritas Prep's 2010 Instructor of the Year, Matt Douglas for GMATT Mondays

Visit the Veritas Prep Blog

Try the FREE Veritas Prep Practice Test
Join the discussion