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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]   

= `4  x 1/6 x 10 x 11 x 21`

= (4 x 5 x 77)

= 1540



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