SOLUTION: After six biology tests, Ruben has a mean score of 73. What score does Ruben need on the next test to raise his average (mean) to 75?

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Question 1133168: After six biology tests, Ruben has a mean score of 73. What score does Ruben need on the next test to raise his average (mean) to 75?
Found 2 solutions by josgarithmetic, greenestamps:
Answer by josgarithmetic(39617) About Me  (Show Source):
Answer by greenestamps(13200) About Me  (Show Source):
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See if this method of solving the problem "works" for you. It is based on the simple concept that the scores below the average must balance with the scores above the average.

The six current scores, with a mean of 73, can be considered as 6 scores of 73 each. The desired new average, 75, is 2 points higher. So, all together, those 6 tests are a total of 6*2 = 12 points below the desired average.

That means the next test has to be 12 points above the desired average.

ANSWER: The required score on the next test is 75+12 = 87.

If you understand this method, you can use it on any similar problem involving the average of a set of numbers that are all relatively close to each other.