Problem: In the sequence 20, 202, 2020, 20202, 202020 …….. each subsequent number is obtained by adding the digit 2 or 0 to the previous number, alternately. Calculate the sum of the digits of the first 100 numbers of that sequence which are divisible by 202
Problem: In the sequence 20, 202, 2020, 20202, 202020 …….. , each subsequent number is obtained by adding the digit 2 or 0 to the previous number, alternately. Calculate the sum of the digits of the first 100 numbers of that sequence which are divisible by 202.
Solution:
The problem is bit lengthy and inviting concentration . It can be solved as in the pictures below;
First Part
Second Part
The answer is clearly have facto 202 – so the sum is divisible by 202 !