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Find the remainder when 1^2 + 2^2 + 3^2 + ... + 50^2 is divided by 15.

 Jul 7, 2021
 #1
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Sum of the  first  n  squares  =    n (n + 1) (2n + 1)   /   6

 

Sum of the first 50  squares  =    50 ( 51) ( 101)   /  6 =   42925

 

42925  mod  15  =     10

 

 

cool cool cool

 Jul 7, 2021

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