CBSE Class 10 Answered
9.If the mean of the following data is 91.Find the missing frequency :-
C. I. Frequency
0-30. 12
30-60. 21
60-90. X
90-120. 52
120-150. Y
150-180. 11
Total 150
Asked by prajapatisohil573 | 02 Aug, 2021, 10:03: AM
Class xi fi fixi
0 - 30 15 12 180
30 - 60 45 21 945
60 - 90 75 x 75x
90 - 120 105 52 5460
120 - 150 135 y 135y
150 - 180 165 11 1815
Total
![sum from blank to blank of f subscript i x subscript i equals 8400 plus 75 x plus 135 y](https://images.topperlearning.com/topper/tinymce/cache/9cdf295f0aaaca4bc76087e971fe978e.png)
![sum from blank to blank of f subscript i equals x plus y plus 96 equals 150](https://images.topperlearning.com/topper/tinymce/cache/97da58ba0b33c090fea093cdc75bd589.png)
![sum from blank to blank of f subscript i x subscript i equals 8400 plus 75 x plus 135 y](https://images.topperlearning.com/topper/tinymce/cache/9cdf295f0aaaca4bc76087e971fe978e.png)
Now, 96 + x + y = 150
Therefore, x + y = 54
![straight x with bar on top equals fraction numerator begin display style sum from blank to blank of end style straight f subscript straight i straight x subscript straight i over denominator begin display style sum from blank to blank of end style straight f subscript straight i end fraction
rightwards double arrow 91 equals fraction numerator 8400 plus 75 straight x plus 135 straight y over denominator 150 end fraction
rightwards double arrow 13650 equals 8400 plus 75 straight x plus 135 straight y
rightwards double arrow 75 straight x plus 135 straight y equals 5250
rightwards double arrow 5 straight x plus 9 straight y equals 350 space space space... space left parenthesis ii right parenthesis
Solving space left parenthesis straight i right parenthesis space and space left parenthesis ii right parenthesis comma space we space get
straight x space equals space 34 space and space straight y space equals space 20](https://images.topperlearning.com/topper/tinymce/cache/e68cf55404756ac867b279634989dae6.png)
Answered by Renu Varma | 02 Aug, 2021, 12:24: PM
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