the sum of 7 numbers. is 133. If one more is added, the mean of the numbers are 20. Find the added number. Question
the sum of 7 numbers. is 133. If one more is added, the mean of the numbers are 20. Find the added number. Question
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Answer:
Given x +y= 7
X cube+ycube=133
We know (x+y)^3=x^3+y^3+3xy(x+y)
Substituting the given, equation becomes
7^3=133+3xy(7)
343=133+21xy
Hence xy=10
We know (x+y)^2=x^2+y^2+2xy
Substitute values of x+y and xy
7^2=x^2+y^2+20
49–20= x^2+y^2
Hence sum of their squares is 29