Question

Sheri's brother gave Sam his collection of stamps when she left for college. At that

time, the value of the collection was $420. Eight years later, the stamp collection
was worth $980. What is the rate of change?

Answer 1

Answer: $70 per year.

Explanation:

Let's say that x is the number of years that has passed and y is how much the stamp is worth.

So we know that in zero years the stamp was worth $420 because that is the time Sheri gave her brother Sam the stamp. That could bring up the coordinates (0,420) .

Now we know that in 8 years it was worth $980 and that could be the coordinates (8,980)

To find the rate of change we need to find the different between the y value and divide it by the difference in the x values.

420 - 980 = -560

0-8 = -8

-560/-8 = 70

The rate of change is 70 which means that it grew by $70 every year.