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JEE Main & Advanced JEE Main Paper (Held On 19 May 2012)

  • question_answer
    The median of 100 observations grouped in classes of equal width is 25. If the median class interval is 20 - 30 and the number of observations less than 20 is 45, then the frequency of median class is     JEE Main  Online Paper (Held On 19  May  2012)

    A) 10

    B)                        20

    C)                        15                          

    D)                        12

    Correct Answer: A

    Solution :

                    Median is given as\[M=l\frac{\frac{N}{2}-F}{f}\times C\]where \[l=\] lower limit of the median - class f = frequency of the median class N = total frequency F = cumulative frequency of the class just before the median class C = length of median class Now, given, \[M=25,N=100,F=45,\] \[C=20-30=10,l=20.\] \[\therefore \]By using formula, we have \[25=20+\frac{50-45}{f}\times 10\] \[25-20=\frac{50}{f}\Rightarrow 5=\frac{50}{f}\Rightarrow f=10\]                


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