The easiest solution is to realize that the first toss doesn't matter. Regardless of whether it comes up heads or tails, you are still on a good path. What is important is that the second and third toss match the first one. What are the chances that the second toss will match the first? Well, there is one chance out of two that it will come up the same. Similarly, the third toss has one chance out of two to come up the same. So the odds that both will occur are 1/2 times 1/2 or 1/4. That's answer choice (B).
An alternate solution is to calculate the chance that the coin will come up heads three times in a row. That chance is 1/2 * 1/2 * 1/2 or 1/8. Similarly, there is a 1/8 chance that tails will come up three times in a row. Once you add those two probabilities, you come up with 2/8, which reduces to 1/4. That's answer choice (B).
Elias Latour
Verbal Specialist @ ApexGMAT
blog.apexgmat.com
+1 (646) 736-7622
