SOLUTION: I want a 75 test average. I will have 3 test grades. I got a 72 and a 76 on the first two tests. What must I make on the third test to recieve a 75 test average?

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Question 1145657: I want a 75 test average. I will have 3 test grades. I got a 72 and a 76 on the first two tests. What must I make on the third test to recieve a 75 test average?
Found 2 solutions by ikleyn, greenestamps:
Answer by ikleyn(52790) About Me  (Show Source):
You can put this solution on YOUR website!
.

MENTAL solution 

To have a 75 test average of 3 tests, you need to have the sum of these three tests as 3*75 = 225.


You just have 72 and 76 in two first tests.


Hence, you need to get  225 - 72 - 76 = 77.    ANSWER


ALGEBRA solution 

%2872+%2B+76+%2B+x%29%2F3 = 75

72 + 76 + x = 3*75 = 225


x = 225 - 72 - 76 = 77.      the same ANSWER

Solved.

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Answer by greenestamps(13200) About Me  (Show Source):
You can put this solution on YOUR website!


When a problem is about averages of numbers that are close together, I find the following method of solving by far the easiest.

Your first test is 1 above the average you want; the second is 3 below.
With those two together, you are 2 points below the average you want.
So your third test needs to be 2 points above the average you want.

ANSWER: 75+2 = 77