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Shauna had an English average of 84%. On her next test she scored 96%, and this raised her overall average to 86%. On the test after this, her average fell to 85%. What was her mark on the last test?

 Mar 27, 2020
 #1
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Check https://www.algebra.com/algebra/homework/Percentage-and-ratio-word-problems/Percentage-and-ratio-word-problems.faq.question.1076070.html

 

Hope this helped!!!

 Mar 27, 2020
 #2
avatar+111321 
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Let  the  number  of  tests  that  she took to  get  the  84 average  =  n

 

So  the  number of  total points she had  was  84n

 

On the next test  she got a  96  and it raised her average  to   86

 

So....we  can solve for n thusly

 

 

84n  + 96

________  =  86          cross-multiply

   n  +  1

 

 

84n + 96  = 86 ( n + 1)    simplify

 

84n  +  96  =  86n + 86        subtract  84n, 86  from both sides

 

10  =  2n    divide both sides  by 2

 

5  = n

 

And let  x  be  the  mark on the last test ......she  has taken 7 tests and we have that

 

84(5)  + 96  +  x

_____________  =    85             cross-multiply    

       7

 

84 (5) + 96 + x  =  85 * 7

 

420 + 96  + x  =  595

 

516  +  x    =  595

 

x =  595  -  516  =   79

 

 

cool cool cool

 Mar 27, 2020
edited by CPhill  Mar 27, 2020
edited by CPhill  Mar 27, 2020

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