What is the probability of NOT tossing two heads on two fair coins?

Answer 1

The probability of tossing two coins one time and not getting two heads is 3/4 or 75%. The possible out comes of this are: HH, HT, TH, TT. There is only one way to get two heads, out of four possible results. Another, faster way to do this problem would be to multiply the probability of getting one head on one coin (1/2) by the probability of getting a head on another coin (also 1/2). This will result in 1/4. Because you want every result BUT this one, subract this answer from one. You will get the an answer of 3/4. This may not seem like a faster method when writing it out, but with a larger number of coins it would save a lot of time, because you do not have to go through all of the combinations.