If you add four numbers together and then divide the sum by 4 you find the a.mean b. weighted average c. median d, mode

The answer is a. mean. This is the same as the average. (The median is different. It is the number in the middle of all the numbers when they are arranged from smallest to largest. There is no summation or division required in order to determine it.)

a.0.8(100 – x) + 0.6x = 100(0.65)

Step-by-step explanation:

The easiest way to find the answer is to derive the equation from the the data given.

The amount of 60% mixture is given as .

The amount of copper from 60% mixture =

The amount of copper from 80% mixture =

Therefore total amount of copper in 100 pound mixture is:

The amount of copper from 60% mixture + The amount of copper from 80% mixture

⇒

We can rearrange the equation as:

Percentage of copper in the final mixture can be derived by:

[Total pounds of copper/Total pounds of the mixture]×100

Percentage of copper in the final mixture is given as 65%

Therefore,

[Total pounds of copper/Total pounds of the mixture]×100=65%

=

This equation can be used to find the value of ..

Therefore the answer is a.0.8(100 – x) + 0.6x = 100(0.65)