Answer:
When you have multiple events (here each flip of the coin is a individual event) the probability of all the events (or the joint probability) is equal to the product of the probabilities of each event.
For example, with a fair coin the probability of getting heads is 0.50
If you get heads 3 times, and you add the probabilities you get:
0-50*3 = 1.50
this has no sense, because the probability must be a number between 0 and 1.
The actual probability is:
P = 0.50*050*0.50 = 0.125
