Exam average

Average of marks that have on the certificates students of 8.A class in mathematics is exactly 2.45. If we did not add 1 and 3 of sutdents Michael and Alena, who arrived a month ago, it would average exactly 2.5.

Determine how many students have class 8.A.

Result

n =  20

Solution:

2.45=Sn 2.5=S13n22.45 = \dfrac{ S}{n} \ \\ 2.5 = \dfrac{S-1-3}{n-2}

n * 2.45 = S
(n-2) * 2.5 = S-1-3

S-2.45n = 0
S-2.5n = -1

S = 49
n = 20

Calculated by our linear equations calculator.



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