Question

find the last didgit of the expression 1^2+2^2+3^2+....+100^2.​

Answer 1

Step-by-step explanation:

first + last together sum up to 1^2 + 99^2 = 100^2 , second and second last the same etc. All the combined 100^2 will have a zero at last digit. Since the list contains 99 numbers, the middle number would be the 50, and 50^2 clearly has a zero as the last digit. Thus, zero will be the last digit.