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प्रश्न
In X standard, there are three sections A, B and C with 25, 40 and 35 students respectively. The average marks of section A is 70%, section B is 65% and of section C is 50%. Find the average marks of the entire X standard.
उत्तर
Here, n1 = 25, n2 = 40, n3 = 35, `bar"X"_1 = 70, bar"X"_2 = 65 and bar"X"_3 = 50`.
Let `bar"X"` denote the average marks of the entire X standard. Then,
`bar"X" = ("n"_1bar"X"_1 + "n"_2 bar"X"_2 + "n"_3 bar"X"_3)/("n"_1 +"n"_2 + "n"_3)`
= `(25 xx 70 + 40 xx 65 + 35 xx 50)/(25 + 40 + 35)`
= `(1750 + 2600 + 1750)/(100)`
= `(6100)/(100)` = 61
Hence, the average marks of the entire X standard is 61%.
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