linear growth model problem?

Question

How do I figure this out?

The number of cars sold weekly by a new automobile dealership grows according to a linear growth model. The first week the dealership sold 2 cars. The second week the dealership sold 6 cars. If the manager gets $100 bonus for every car sold, how much total bonus money did the manager make in the first four weeks?

Answer 1

The growth is linear, so the number of cars sold increases by the same amount each week. That's four cars per week.
Week 1 - 2 cars
Week 2 - 6 cars
Week 3 - 10 cars
Week 4 - 14 cars

So the total number of cars sold in the first four weeks is 32.

If the manager gets $100 per car sold, he gets $3200.

Answer 2

If you're talking linear growth as a fixed rate of increase over time, you're increase would be 4 cars per week. You might assume a three-fold increase, but that wouldn't be linear. So 2 cars in week 1, 6 in week 2, 10 in week 3, and 14 in week 4. Add up all the cars sold (because you want to know how much he made in the first 4 weeks) and you get 32. 32 x $100 = $3,200.
Fair pay for a week (before taxes, though).

Answer 3

First week he gets $200
Second week, he gets $600

Because it is linear, it increases by the same amount every week (or, $400 / week)

Third week, he gets $1000
Fourth week, he gets $1400

Now add up the amounts.