(11^2+12^2+13^2+......+20^2)=? Options:
A) 385 B) 2485 C) 2870 D) 3255 E) None of them
=(1^2+2^2+3^2+......+30^2)-(1^2+2^2+3^2+......+10^2)   =(20x21x41/6 - 10x11x21/6)   Therefore, (1^2+2^2+....+n^2)=1/6n(n+1)(2n+1)   =(2870-385)= 
<gadget id="calculator">(2870-385)</gadget>
<output>2_485</output>
2485.   Answer is 2485
<result>B</result>
(11^2+12^2+13^2+......+20^2)=?