Since you end up with 40% MORE every ten days, the common ratio is actually 1.4, not 0.4. Also, since your unit of time is "every 10 days", for 100 days, that means n is 10, since 10x10 = 100.
An advertising company designs a campaign to introduce a new product to the city. The company determines that 1000 people are aware of the product at the beginning of the campaign. The number of new people aware increases 40% ever 10 days. What is the total number of people who are aware after 100 days?
My attempt:
t1 = 1000 r = 0.40 per 10 days n = 100
0.40 / 10 = .04 per day
r = .04
Sn = t1r^n - 1 / r - 1
S100 = (1000)(.04^100) - 1 / .04 - 1
S100 = .96153...
The correct answer is 98,739, I am WAY off. Can someone please help me, I am really confused...