Guide 5, Chapter 7, Pg. 139

[Jmoustafa345]

Hello! I'm having trouble wrapping my head around question 7 on pg. 139. I can't see how it's different than the question they ask on pg. 129 (which I'm having trouble with, too!), and why the two are solved differently.

[tommywallach]

Hey J,

Well, they're very different questions. The one on 129 is very specific: we want to know the odds of EXACTLY two heads. The one on 139 is happy with ANY time we have more heads than tails. There are three results that make this happen:

3 heads, 2 tails
4 heads, 1 tail
5 heads, 0 tails

Now, we could attempt to solve for all three of these separately and add them up, but that would be a waste of time, because we know there are only TWO possibilities. Either we get more HEADS than TAILS, or we get more TAILS than HEADS. You might be thinking: "What if they tie?" But you can't tie when you're flipping a coin five times. You can tie when you're flipping a coin SIX times (3 heads, 3 tails), but not FIVE (or any odd # of flips, for that matter). So the answer is (C), and we don't have to do any work at all!

-t