SOLUTION: If the average of 7 quizzes is 15, what dose AJO have to get on her 8th quiz to raise her average to 16

Algebra ->  Average -> SOLUTION: If the average of 7 quizzes is 15, what dose AJO have to get on her 8th quiz to raise her average to 16      Log On


   

Question 867775: If the average of 7 quizzes is 15, what dose AJO have to get on her 8th quiz to raise her average to 16
Answer by jim_thompson5910(35256) About Me  (Show Source):
You can put this solution on YOUR website!
Let x = score on 8th quiz


"the average of 7 quizzes is 15" so S/7 = 15 where S is the sum of the 7 quiz scores. Solve for S to get S = 7*15 = 105


Now add on the last quiz score x to S and then divide by 8 to get the new average 16 %28S%2Bx%29%2F8+=+16


%28S%2Bx%29%2F8+=+16


%28105%2Bx%29%2F8+=+16 Plug in S = 105. Solve for x


105%2Bx+=+16%2A8


105%2Bx+=+128


x+=+128-105


x+=+23


She needs to get a 23 on the 8th quiz.