SOLUTION: (Please show steps and explain): Namid had an average of 74 on four history tests. What score does he have to get on the 100-point final exam if it counts double and he wants to

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Question 4636: (Please show steps and explain):
Namid had an average of 74 on four history tests. What score does he have to get on the 100-point final exam if it counts double and he wants to have an average of 80 or better?
Answer by longjonsilver(2297) About Me  (Show Source):
You can put this solution on YOUR website!
on the 4 test so far, he has averaged 4*74 --> 296 marks out of 400.

We need to find the score on the final exam (out of 100) to bring his average up to 80% or better. And this final exam is counted double:

so, %28%28296%2Bx%2Bx%29%2F600%29%2A100+=+80
%28%28296%2B2x%29%2F6%29+=+80
%28296%2B2x%29+=+480
2x = 480-296
2x = 184
so x = 92

jon