Question

a tank is filling up at a constant rate. the number of gallons of water in the tank, y, after it has been filling up for x minutes is given in the table below.

time (minutes)	water (gal)
20	45.9
30	59.2
40	72.5

what is the rate of change of the represented in the table?
-1.33 gallons per minute
1.33 gallons per minutes
13.3 gallons per minutes
0.33 gallons per minute

Explanation:

Step1: Recall rate - of - change formula

The rate of change (slope) formula between two points $(x_1,y_1)$ and $(x_2,y_2)$ is $m=\frac{y_2 - y_1}{x_2 - x_1}$. Let's take two points from the table, say $(x_1 = 10,y_1=32.6)$ and $(x_2 = 20,y_2 = 45.9)$.

Step2: Substitute values into formula

$m=\frac{45.9 - 32.6}{20 - 10}=\frac{13.3}{10}=1.33$.

Answer:

1.33 gallons per minute