How do I solve this problem?

Question

Computer use around the world has risen 19% anually since 1980

If 18.9million computers were in use in 1980, Write an equation for the number of computers in use for t years after 1980.

Answer 1

Let y = the number of computer users at year t. 19% growth per year is an exponential growth, so we want to use the exponential equation which has the form:

y = a·b^t

where:

1. y = computer users at year t
2. a = initial number of computer users in 1980 = 18.9 million
3. b = (1+ growth rate) = 1 + 0.19 = 1.19
4. t = years since 1980

y = a·b^t

y = 18.9·(1.19)^t