Question

xi 's are the midpoints of the class interval of grouped data , fi 's are the corresponding frequencies and x is the mean then find Σ(fixi - x).
(Class 10 Maths Sample Question Paper)
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Answer 1

Answer:

Given that, xi are the mid points of the class intervals.

fi are the corresponding frequencies.

The mean xˉ for the grouped data is xˉ=n∑fixi

⟹xˉn=∑fixi ------(1)

∑(fixi−xˉ)=∑fixi−∑xˉ

⟹∑(fixi−xˉ)=xˉn−∑xˉ (from (1))

⟹∑(fixi−xˉ)=xˉn−xˉn=0