Multiple Choice Questions

If the mean of a b c is M and ab bc ca 0 then the mean of a2 b2 c2 is ........

Qunatitative Aptitude (RBI Ast) Average

If the mean of a, b, c is M and ab + bc + ca = 0, then the mean of a^2, b², c² is

M²

3 M²

6 M²

9 M²

( a + b + c) / 3 = M or (a + b + c) = 3M.

Now. (a+b+c)² = (3M)²= 9M^{2 .}

a²+b²+c²+2(ab+bc+ca) = 9M²

a²+b²+c²=9M² ,(ab+bc+ca=0)

Required mean = (a²+b²+c²) = 9M²= (3M)^{2 .}

Hence, option 2 is the correct answer.

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