Matthew has recorded the amount he's saved every three months. months savings 3 $1,800 6 $3,600 9 $5,400 christopher saves $550 every month. assume that matthew and christopher both save money at constant rates. whose unit rate is higher, and by how much?

The correct answer is:

Matthew's rate is higher by $50 per month.

Explanation:

We know that Christopher's rate is $550 per month.

To find Matthew's rate, we will treat the data we have as ordered pairs:
(3, 1800)
(6, 3600)
(9, 5400)

We find the slope of the line between these points.  The formula for slope is:



Using the first two points, we have:


To verify Matthew saves the same amount each month, we will find the slope between the second two points and make sure they're the same:



Matthew's rate is $600 per month.
This is higher than Christopher's by 600-550=$50 per month.