Solve a Coin Problem
Using Pascal's Triangle
Suppose I flip a coin repeatedly. On each flip I get either a Head (H) or a Tail (T).
If I throw the coin once then two results are possible. I could get 1 H or I could get 1 T.
If I throw the coin twice, four outcomes are possible: I could get either HH, HT, TH, or TT.
 HH |
 HT |
 TH |
 TT |
In this case, we have 1 outcome that gives us 2 Heads, 2 outcomes that give us 1 Head and 1 Tail, and 1 outcome that gives us 2 Tails.
If I tossed the coin 7 times, how many possible outcomes would have 4 Tails and 3 Heads?
email the author: Bruce Jacobs
Last modified: Thursday, February 6, 2003