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GeneralRe: Mental arithmetic Pin
Member 1157700818-Aug-20 2:06
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GeneralRe: Mental arithmetic Pin
Jörgen Andersson18-Aug-20 3:59
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GeneralRe: Mental arithmetic Pin
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GeneralRe: Mental arithmetic Pin
avanishrayankula18-Aug-20 5:01
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GeneralRe: Mental arithmetic Pin
Member 1146760818-Aug-20 6:04
MemberMember 1146760818-Aug-20 6:04 
This is how I mentally solved it. Well, I used my fingers, also.

10^2 + (10 + 1)^2 + ... + (10 + 4)^2

taking into account (a + b)^2 = a^2 + 2ab + b^2, we have

10^2 appears 5 times: 500
the 2ab term gives:
2 * (10*1 + 10*2 + 10*3 + 10*4) = 20 * (1 + 2 + 3 + 4) = 200; 700, up to now
then, the sum of the squares:
1^2 + 2^2 + 3^2 + 4^2 = 1 + 4 + 9 + 16 = 30.
numerator sums 730. denominator: 350 + 15, times two gives 700 + 30;

answer: 2
GeneralRe: Mental arithmetic Pin
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