What are the last 2 digits of the sum 1 + 11 + 111 + ... + 111...111 (last one has 50 digits)?
This is a question from Junior Math Olympiad. Question : What are the last 2 digits of the sum 1 + 11 + 111 + ... + 111...111 (last one has 50 digits)? Solution : Here is tiny python program. Also available http://www.codeskulptor.org/#user43_XiVvNuzfshT3lKX.py # What are the last 2 digits of the sum # 1 + 11 + 111 + ... + 111...111 (last one has 50 digits? total_num = 50 this_num = 0 sum = 0 for i in range(total_num): this_num = 10 ** i + this_num print "Number " + str(i+1) +":", this_num sum = sum + this_num print "Total Sum:", sum Output: Number 1: 1 Number 2: 11 Number 3: 111 Number 4: 1111 Number 5: 11111 Number 6: 111111 Number 7: 1111111 Number 8: 11111111 Number 9: 111111111 Number 10: 1111111111 Number 11: 11111111111 Number 12: 111111111111 Number 13: 1111111111111 Number 14: 11111111111111 Number 15: 1111111111...