You are having a pool party and invite 2 of your best friends. These two friends each invite two other people. Each of these 2 people invite 2 people that haven't been invited. How many people will be invited if this process continues for four rounds?

Answer 1

number of people invited in round 1 = 2
number of people invited in round 2 = 4
.....

total invited = 2 + 4 + ....

Answer 2

40