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Question


(22 + 42 + 62 + ... + 202) = ?

Options:
A .  770
B .  1155
C .  1540
D .  385 x 385
Answer: Option C

(22 + 42 + 62 + ... + 202) = (1 x 2)2 + (2 x 2)2 + (2 x 3)2 + ... + (2 x 10)2


= (22 x 12) + (22 x 22) + (22 x 32) + ... + (22 x 102)


= 22 x [12 + 22 + 32 + ... + 102]



(22 + 42 + 62 + ... + 202) = ?
Ref: (12 + 22 + 32 + ... + n2) =
1
n(n + 1)(2n + 1)
(22 + 42 + 62 + ... + 202) = ?
   
6



=
(22 + 42 + 62 + ... + 202) = ?
4 x
1
x 10 x 11 x 21
(22 + 42 + 62 + ... + 202) = ?
6


= (4 x 5 x 77)


= 1540.



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