Shauna had an English average of 84%. On her next test she scored 96%, and this raised her overall average to 86%. On the test after this, her average fell to 85%. What was her mark on the last test?
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+128475 Let the number of tests that she took to get the 84 average = n
So the number of total points she had was 84n
On the next test she got a 96 and it raised her average to 86
So....we can solve for n thusly
84n + 96
________ = 86 cross-multiply
n + 1
84n + 96 = 86 ( n + 1) simplify
84n + 96 = 86n + 86 subtract 84n, 86 from both sides
10 = 2n divide both sides by 2
5 = n
And let x be the mark on the last test ......she has taken 7 tests and we have that
84(5) + 96 + x
_____________ = 85 cross-multiply
7
84 (5) + 96 + x = 85 * 7
420 + 96 + x = 595
516 + x = 595
x = 595 - 516 = 79
