Question

What is the last digit of the number equal to
the sum 1 + 6 +6^2 +.............+ 6^100?
(A) 0
(B) 1
(C) 2.
(D) 6​

Answer 1

Answer:

6^1=6;

6^2=36;(which is basically 6*6=36)

6^3=216;(36*6=216)

Going by that , every power of 6 will have 6 as it's last digit.

We will then have hundred 6’s as last digit.(as there are hundred 6 with powers)

Since the last digit of the number of the given sum will be summation of those 6s.

We then have 6*100+1 =1.

So,the final answer 1.