P(A and B)=P(A)* P(B)
From the exercise, we know that the probability of landing on heads is 0.8. Now we can calculate the probability that Earl will have to do both chores. In other words, we can find the probability that he lands on heads twice.
b Let's illustrate the different outcomes with a tree diagram. Assume that the first coin toss decides whether or not Earl has to take out the garbage. The second toss decides if he needs to do the dishes. The highlighted path shows the outcome that results in garbage duty but no need to wash the dishes.
Again, to calculate the probability of this event, we have to use the Multiplication Rule of Probability.