Let 75.....57 denote the (r + 2) digit number where the first and the last digits are 7 and the remaining r digits are 5.

Question

Let  denote the (r + 2) digit number where the first and the last digits are 7 and the remaining r digits are 5. Consider the sum S = 77 + 757 + 7557 + …+ . If S = , where m and n are natural numbers less than 3000, then the value of m + n is ______.

Answer 1

\(\therefore m + n = 1219\)