Question

9. Suppose that five people are ill during the first week of an epidemic and each sick person
spreads the contagious disease to four other people by the end of the second week and
so on. By the end of 15th week, how many people will be affected by the epidemic?

Answer 1

Hi,
5 ill week 1, each spreading to 4 people by the end of the next week...
By the end of the tenth week of the epidemic, how many people have been

affected by the illness?
{5,20,80,320,...}
Geometric sequence r = 4

= a(1-r^n)/(1-r)= 5(1-4^10)/(1-4) = 1,747,625