College Algebra

Question

Online Shopping In 2011 online sales were $192 billion, and in 2014 they were $249 billion. (Source: Forrestor Forecast.)

1. Find a linear function S that models these data. Write S(x) in slope-intercept form.
2. Interpret the slope of the graph of S.
3. Determine when online sales were $230 billion.

Answer 1

S=(77/3)(x-2011) + 192

the slope is how much sales increase each year = 25 2/3 billion

Let S = 230 and plug into the equation and solve for x

230=(77/3)(x-2011) + 192

(77/3)(x-2011) = 230-192 = 38

x-2011 = 38(3/77) = 114/77 = 1 37/77 years

x = 2012 + almost 6 months. That makes sales reach $230 billion in 2013