Question

A coin is tossed seven times and the sequence of heads and tails is observed. what is the number of different outcomes having exactly three​ heads?

Answer 1

You could make a tree diagram
H T ← 1st toss

H T H T ← 2nd toss

H T H T H T H T ← 3rd toss
etc ,,, then count the combination of favorable outcomes

Using a calculator:
Total number of outcomes is
`2^(7)` = 128
Probability of getting exactly 3 heads is found using the follow calculator feature: binompdf(7, 0.5, 3)

ANSWER: Typed into the calculator as follows binompdf(7,0.5,3)×128 = 35