Question

A store had 175 cell phones in the month of January. Every month, 10% of the cell phones were sold and 10 new cell phones were stocked in the store.

Which recursive function best represents the number of cell phones in the store f(n) after n months?

f(n) = 175 − 0.9 x f(n − 1) + 10, f(0) = 175, n > 0
f(n) = 0.1 x f(n − 1) + 10, f(0) = 175, n > 0
f(n) = 175 + 0.9 x f(n − 1) + 10, f(0) = 175, n > 0
f(n) = 0.9 x f(n − 1) + 10, f(0) = 175, n > 0

Answer 1

What do you think the answer is?

Plug in n=1, 2, etc and see which one gives you the right answer.