I have 7.5 quarts of fluid that needs changed; however, the fluid can only be removed and replaced 2.5 quarts at a time. How many 2.5 quart changes do I need to make to have 80% or more new fluid?

Number of times to change fluid = 3

Step-by-step explanation:

The amount of fluid that needs to be changed is 7.5 quarts.

The fluid can only be removed and replaced 2.5 quarts at a time.

How many 2.5 quart changes do we need to have 80% or more new fluid?

Lets first find out the 80% amount of the fluid that needs to be changed.

80% amount of fluid = 0.80*7.5

80% amount of fluid = 6 quarts

Now let us find out the number of times required to change the fluid.

Number of times = 6 quarts/2.5 quarts

Number of times = 2.4

We cannot have number of times in fraction so we can either go with 2 times or 3 times, since 2 times is not enough to make 80% or more new fluid, we must change the fluid 3 times, therefore the required number of times to change the fluid is

Number of times to change fluid = 3