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Asked by Harsh

Feb 9, 2014

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 |

Syeda

Member since Jan 25, 2017

Answer.

Given, mean = 50.25

Sum of observations = 80

That is (60 + x + y) = 80

(x + y) = 20 â€¦ (1)

Mean = (2880 + 45x + 75y)/80

That is (50.25 Ã— 80) = 2880 + 45x + 75y

4020 â€“ 2880 = 45x + 75y

45x + 75y = 1140

3x + 5y = 76 â€¦ (2)

On solving (1) and (2), we get

x =2 and y = 18

Given, mean = 50.25

Sum of observations = 80

That is (60 + x + y) = 80

(x + y) = 20 â€¦ (1)

Mean = (2880 + 45x + 75y)/80

That is (50.25 Ã— 80) = 2880 + 45x + 75y

4020 â€“ 2880 = 45x + 75y

45x + 75y = 1140

3x + 5y = 76 â€¦ (2)

On solving (1) and (2), we get

x =2 and y = 18

Kishore Kumar

Member since

Given, mean = 50.25

Sum of observations = 80

That is (60 + x + y) = 80

(x + y) = 20 â€¦ (1)

Mean = (2880 + 45x + 75y)/80

That is (50.25 Ã— 80) = 2880 + 45x + 75y

4020 â€“ 2880 = 45x + 75y

45x + 75y = 1140

3x + 5y = 76 â€¦ (2)

On solving (1) and (2), we get

x =2 and y = 18