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Asked by Harsh

Feb 9, 2014

Find the missing frequencies in the following frequency distribution

Find the missing frequencies in the following frequency distribution if the mean is 50.25 and the total no of students in the class is 80.
Marks obt.(%) 25 35 45 55 65 75 85
No. of students 7 23 x 15 10 y 5

Answers(2)

Answer

Kishore Kumar


Given, mean = 50.25
Sum of observations = 80
That is (60 + x + y) = 80
(x + y) = 20 … (1)
Mean = (2880 + 45x + 75y)/80
That is (50.25 × 80) = 2880 + 45x + 75y
4020 – 2880 = 45x + 75y
45x + 75y = 1140
3x + 5y = 76 … (2)
On solving (1) and (2), we get
x =2 and y = 18

Syeda

Member since Jan 25, 2017

Answer.
Given, mean = 50.25
Sum of observations = 80
That is (60 + x + y) = 80
(x + y) = 20 … (1)
Mean = (2880 + 45x + 75y)/80
That is (50.25 × 80) = 2880 + 45x + 75y
4020 – 2880 = 45x + 75y
45x + 75y = 1140
3x + 5y = 76 … (2)
On solving (1) and (2), we get
x =2 and y = 18
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