SOLUTION: Please double check my work Bill needs an average of 80 on four tests in science to make the honor roll. What is the lowest score he can receive on hte fourth test if his first

Question 171643This question is from textbook
: Please double check my work
Bill needs an average of 80 on four tests in science to make the honor roll. What is the lowest score he can receive on hte fourth test if his first three scores are 73, 96, and 89?
I added 73+96+89 = 258
then I divided 258/3 and came up with the answer of 86
86 is the lowest grade he can make
did I do this right? This question is from textbook

Found 2 solutions by nerdybill, Earlsdon:
Answer by nerdybill(7384) (Show Source): You can put this solution on YOUR website!
You did NOT consider the fourth test!
.
Goal average 80 on four tests
Let x = grade on fourth test
total on last three tests
73+96+89 = 258
.
(258+x)/4 >= 80
258+x >= 320
x >= 62
.
He has to get a grade equal or greater than 62

Answer by Earlsdon(6294) (Show Source): You can put this solution on YOUR website!
Er...not quite!
You must add all four of the scores, even the unknown one (x) and then divide by 4 to get the expected average of 80.
Note! means "y is at least 80".
Multiply both sides by 4.
Subtract 258 from both sides.

Bill needs to score at least 62 on his fourth test to achieve an overall average of at least 80.
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