math
posted by helpme on .
hi i did this problem and i just want to know if its right.
3 coins are flipped , find the following probabilities:
a) P(2 heads)
b) P( at most 2 heads)
c) P(no heads)
i got
a) 1/4
b) .75
c) 5/8

There are 8 possible outcomes
HHH TTT
HHT TTH
HTT THH
HTH THT
a) wrong 3 out of 8 have two heads
b) wrong. "At most two" is the same as "not three heads" 7 out of 8 don't have three heads.
c) wrong again "no heads" is the same as "all tails"