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Evian's average on five tests was 90%. The average of the four highest test scores was 93%, and the average of the four lowest test scores was 87.75%. What was the sum of the lowest mark and the highest mark? 

 Feb 25, 2019
 #1
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(h + s + l )/5 = 90           or     h+s+l = 450                    where h = hi score   s = 3 middle scores    l = low score

 

(h +s)/4 = 93          or      h+s = 372        or       h= 372-s      

  and

(l+s)/4 =87.75        or      l+s  = 351         or      l = 351-s

 

Take the last  2 red equations and sustitute into the first red equation:

 

372-s     +   s      +   351-s  = 450

s=273

 

Now    (l +s)/4 = 87.75      so   l = 78

 and    (h+s)/4 = 93           so   h = 99                 h+l = 177

 Feb 25, 2019

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