Problem Solving (PS) | Find the last digit of the number 1^2 + 2^2 + ... + 99^2 ?

Breaking Down theInfo:

Include\(0^2\) in the sum as well (which will not change the last digit), then we can bracket the numbers in groups of 10 numbers each, each with the last digit same as the one for\( 0^2 + 1^2 + 2^2 + ... +9^2\) . There are 10 such brackets like this.

If the last digit of this sum is X, then 10 sums of these would have the last digit same as 10X, which ends in an 0 so the last digit must be 0 for
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