10 % of 10 + 20 % of 20 + 30 % of 30 + 40 % of 40 + ......+ 100 % of 100 is equal to

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19 Jun 2012 percentage

10 % of 10 + 20 % of 20 + 30 % of 30 + 40 % of 40 + ......+ 100 % of 100
is equal to

OPtion

1) 312
2) 345
3) 356
4) 385
5) 398
6) 423
7) 435
8) 456
9) 478
10) none of these

Solution

10*10/100 + 20*20/100 + .........
=1^2 + 2^2 + 3^2 + ...............+10^2
=10*11*21/6 = 385
here we use formula
sum of squares of first n natural numbers = n*(n+1)*(2n+1)/6

Correct Option: 4 Best Solution (0)