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You look like you could use a shmoopy question...On her first four tests, Jenny earned an 85,
97, 79, and 84. Her uber-strict parents aren't letting her
attend the State Math Finals unless she brings her overall mean up to at least 87.
What must Jenny earn on her next test to be allowed to have... every young girl's dream
come true? And here are the potential answers...
OK so what is this question asking?
Well it's really the advanced ninja version of taking averages.
To solve, first assess where we are; Jenny took 4 tests and she's going to take another
-- she will have taken 5 tests in total.
And the TOTAL of these 5 tests must have an average of 87 -- or in other words, they
must total to 5 times 87 or have a total of 435.
So the answer comes from just adding up the previous 4 tests, subtracting that number
from 435 and whatever is left is what she has to get to average an 87.
Cool so far?
So if we add the previous 4 tests we get a sub-total of 345.
Subtract 345 from 435 and we get 90.
So she has to get a 90 on the last test.
As in, "Deadly weapons."