1. The problem statement, all variables and given/known data Toss a coin 3 times. What is the probability that we get a head on the first toss or a head on the second toss or a head on the third toss? 2. Relevant equations Pr(AorB)=Pr(A)+Pr(B)-Pr(AandB) 3. The attempt at a solution A=head on 1st toss B=head on 2nd toss C=head on 3rd toss Pr(AorBorC)=Pr(A)+Pr(B)+Pr(C)-Pr(A&B&C) =(1/2)+(1/2)+(1/2)-(1/8)=11/8 but 11/8>1 which is a contradiction. So something is wrong with my sol.