SOLUTION: A student received scores of 72, 85, 53 and 80 on the first four quizzes. What minimum score does the student need on the fifth quiz to average 70 for all 5 quizzes?

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Question 896556: A student received scores of 72, 85, 53 and 80 on the first four quizzes. What minimum score does the student need on the fifth quiz to average 70 for all 5 quizzes?
Found 2 solutions by vja_1994, richwmiller:
Answer by vja_1994(6) About Me  (Show Source):
You can put this solution on YOUR website!
First add all the received scores:
72%2B85%2B53%2B80=290
Let x be the score of the fifth quiz.
We know the student wants an average of 70 for all 5 quizzes, yet he has only taken 4 quizzes.
(Average of 5 quizzes)=(total score of all 5 quizzes)/(# of quizzes)
When you plug in the values you know it will look like this:
70=%28%28290%2Bx%29%2F5%29
Solve for x:
Multiply each side of the equation by 5.
70%2A5=%28%28290%2Bx%29%2F5%29%2A5
350=290%2Bx
Subtract 290 from each side of the equation.
350-290=%28290%2Bx%29-290
60=x
The student will need a 60 on his fifth quiz to achieve an average of 70 for all 5 quizzes.
-Alejandro

Answer by richwmiller(17219) About Me  (Show Source):
You can put this solution on YOUR website!
another way
72-70=2
85-70=15
53-70=-17
80-70=10
for a difference of +10
x-70=-10
x=60
72-70=2
85-70=15
53-70=-17
80-70=10
60-70=-10
for a difference of 0
72+ 85+ 53 + 80+60=350
350/5=70