SOLUTION: emilys test grades are 69, 71, and 67. she wants to bring up her average to a 70. what must she score on her next testing order to have exactly a 70% average?? can you break this

Algebra ->  Average -> SOLUTION: emilys test grades are 69, 71, and 67. she wants to bring up her average to a 70. what must she score on her next testing order to have exactly a 70% average?? can you break this      Log On


   



Question 663839: emilys test grades are 69, 71, and 67. she wants to bring up her average to a 70. what must she score on her next testing order to have exactly a 70% average??
can you break this down for me the parent so i can explain to my son please thank you

Answer by vleith(2983) About Me  (Show Source):
You can put this solution on YOUR website!
Let TestScore4 be the test score on the test that will give Emily an average of 70 across all four test
Average is given by the TestSumTotal/NumberOfTestsTaken
Average+=+%28TestScore1+%2B+TestScore2+%2B+TestScore3+%2B+TestScore4%29%2F4
70+=+%2869+%2B+71+%2B+67+%2B+TestScore4%29%2F4
280+=+%2869+%2B+71+%2B+67+%2B+TestScore4%29
280+-+69+-+71+-+67+=+TestScore4
73+=+TestScore4
Make sense?