SOLUTION: Suppose a student has earned the following grades on her first four quizzes: 83, 72, 89, 78. What must she score on her fifth quiz in order to have a mean of 80 on all of her quizz

Algebra ->  Average -> SOLUTION: Suppose a student has earned the following grades on her first four quizzes: 83, 72, 89, 78. What must she score on her fifth quiz in order to have a mean of 80 on all of her quizz      Log On


   

Question 765737: Suppose a student has earned the following grades on her first four quizzes: 83, 72, 89, 78. What must she score on her fifth quiz in order to have a mean of 80 on all of her quizzes?
Answer by MathLover1(20850) About Me  (Show Source):
You can put this solution on YOUR website!

Let x = score on the 5th quiz to have an 80 average
if first four quizzes are 83, 72, 89, 78, then
%2883%2B72%2B89%2B78%2Bx%29%2F5=80 .....solve for x
83%2B72%2B89%2B78%2Bx=80%2A5
322%2Bx=400
x=400-322
x=78.... she must score 78 to have an average of 80