SSC CGL Model Paper 1

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Question : 54 of 100

Marks: +1, -0

A man paints 'n' squares with sides 1,2,3 ....n cm respectively. The average area painted by the man is (in cm

^{2}

) :

$(n + 2 )/2$
${(n -1)(n + 2 )}/6$
n
${(n +1)(2 n + 1)}/6$

Solution:

Area of square

= 1 ^2+2^2 +3^2 +....n^2

Sum of squares of 'n' natural no. =

{n(n +1)(2 n + 1)}/6

Average

=\sum/n={n(n +1)(2 n + 1)}/{6n}

={(n +1)(2 n + 1)}/6

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