Question

A store had 235 MP3 players in the month of January. Every month, 30% of the MP3 players were sold and 50 new MP3 players were stocked in the store. Which recursive function best represents the number of MP3 players in the store f(n) after n months? f(n) = 0.7 x f(n − 1) + 50, f(0) = 235, n > 0 f(n) = 237 − 0.7 x f(n − 1) + 50, f(0) = 235, n > 0 f(n) = 0.3 x f(n − 1) + 50, f(0) = 235, n > 0 f(n) = 237 + 0.7 x f(n − 1) + 50, f(0) = 235, n > 0

Answer 1

Answer is A)
f(n) = 0.7 x f(n − 1) + 50, f(0) = 235, n > 0

This demonstrates the 30% decrease in the stock by multiplying the previous month's number by .7, and also adds 50 mp3 players each month.
Plugging in the first month:
f(1) = .7 * 235 + 50
f(1) = 165 + 50 = 215
This is consistent with a 30% decrease in the stock, plus 50.