SEAMO 2027 - Paper B - SET 06 - Self-study Question 13

A palindromic pair here means two numbers whose digits are reversed, for example 13 and 31, 56 and 65, or 92 and 29. How many pairs of two-digit numbers of this kind have sum 99?

Count an unordered pair once: for example, 13 and 31 is the same pair as 31 and 13.