A water tank has 155 gallons of water in it. Sam begins to empty it at the rate of 8 gallons per minute. Write an equation and then graph.

Question

I believe it has to be in the formula of y=mx+b.

Answer 1

For this one, I presume that you are supposed to determine the amount of water in the tank after a certain number of minutes. Since we don't have a specific number of minutes, we will let that be x (since x is can be any value). So, after x minutes, the tank has lost 8x gallons from the original 155. (Ex. If x =2 minutes, the tank lost 2*8 or 16 gallons).

 

So, f(x) = 155 - 8x, where f(x) is the number of gallons remaining after x minutes and x is the number of minutes.

 

To get this in slope-intercept form all the way, simply use the associative property of addition to move your terms around:

 

f(x) = 155 - 8x

f(x) = 155 + (-8x)

f(x) = -8x + 155

Answer 2

Are we writing an equation showing the amount of water left in the tank as a function of time in minutes? If so,

y = -8x + 155 

m = -8

y-intercept = 155

x-intecept = 19.4 (rounded to the nearest tenth)

Now, you can easily graph this equation.