=>
11^2 + 12^2 + … + 20^2
= ( 1^2 + 2^2 + … + 20^2 ) – (1^2 + 2^2 + … + 10^2)
= 20∙21∙41/6 - 10∙11∙21/6
= 2870 – 385
= 2485
Ans: D
11^2 + 12^2 + … + 20^2
= ( 1^2 + 2^2 + … + 20^2 ) – (1^2 + 2^2 + … + 10^2)
= 20∙21∙41/6 - 10∙11∙21/6
= 2870 – 385
= 2485
Ans: D
