There are three classes of form four
which are 4a, 4b and 4c.
in mathematics result the arithmetic mean of
4a 4b and 4c are 70, 60 and 80 and their
standard deviation are 3, 3.4, and 2.5
Find the arithmetic mean and standard deviation when
we combine the results of mathematics for
all classes of form four. Assuming the
number of students of
4a,4b and 4c are 30,45,25.
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