I know how to find the average but the 3 times the quiz grade is confusing me.

Question

You want to earn an A(90% or greater in a class. Your grade is based on the average of 5 quizzes and a final exam. The quizzes are weighted evenly and your final exam is weighted as 3 quiz grades. Your quiz grades are: 92, 84, 99, 87, 100. What grades can you get on your final exam and still get and "A" in the class? Write an inequality and solve. Write a sentence that explains your answer.

Answer 1

Your average is equal to (92 + 84 + 99 + 87 + 100 + X + X + X) /8  >= 90

 

We can write the equation like this because we can replace your final exam with three equivalent quiz grades and just include them with the rest. 

 

Now we just solve for X,

 

(92 + 84 + 99 + 87 + 100 + 3X) >=90*8

462 + 3X >= 720

3X >= 258

X >= 86

 

So if you get an 86 or higher on your final exam, your average will be a 90 or higher.