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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
Expert Answer
   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 equals x plus y plus 96 equals 150     sum from blank to blank of f subscript i x subscript i equals 8400 plus 75 x plus 135 y
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
Answered by Renu Varma | 02 Aug, 2021, 12:24: PM
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