SOLUTION: The average grade of Folly in his 6 subjects is 83.45. What grade must he have in his 7th subject so that he will have the average of 85? Thank you

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Question 1121565: The average grade of Folly in his 6 subjects is 83.45. What grade must he have in his 7th subject so that he will have the average of 85? Thank you
Found 4 solutions by Stitch, ankor@dixie-net.com, Alan3354, MathTherapy:
Answer by Stitch(470) About Me  (Show Source):
You can put this solution on YOUR website!
Let C = The current grade sum of his previous 6 tests.
Let G = Be the grade needed on the 7th test

We can now write two equations.
Equation 1: C%2F6+=+83.45
Equation 2: %28C%2BG%29%2F7+=+85
Lets start by solving equation 1 for C:
C%2F6+=+83.45
Multiply both sides by 6
6%2A%28C%2F6%29+=+83.45%2A6
Simplify
highlight%28C+=+500.7%29
Now plug 500.7 into equation 2 for C
Equation 2: %28C%2BG%29%2F7+=+85
%28500.7%2BG%29%2F7+=+85
Multiply both sides by 7
7%2A%28500.7%2BG%29%2F7+=+85%2A7
Simplify
500.7%2BG+=+595
Subtract 500.7 from both sides.
highlight_green%28G+=+94.3%29
Folly will have to get a score of 94.3 on the next test.

Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
You can put this solution on YOUR website!
The average grade of Folly in his 6 subjects is 83.45.
Find the total grade for these 6 subjects
6 * 83.45 = 500.7
What grade must he have in his 7th subject so that he will have the average of 85?
let x = the grade of the 7th subject
%28%28500.7%2Bx%29%29%2F7 = 85
500.7 + x = 85 * 7
x = 595 - 500.7
x = 94.3

Answer by Alan3354(69443) About Me  (Show Source):
You can put this solution on YOUR website!
The average grade of Folly in his 6 subjects is 83.45. What grade must he have in his 7th subject so that he will have the average of 85?
-------
(6*83.45 + G)/7 = 7*85

Answer by MathTherapy(10556) About Me  (Show Source):
You can put this solution on YOUR website!

The average grade of Folly in his 6 subjects is 83.45. What grade must he have in his 7th subject so that he will have the average of 85? Thank you
matrix%281%2C3%2C+%286%2883.45%29+%2B+S%29%2F7%2C+%22=%22%2C+85%29

Solve for S, the 7th-subject score to get your answer.