A student finds the average of nine positive integers

A student finds the average of nine positive integers. Each integer contains two digits. By mistake, the boy interchanges the digits of one number say pq for qp. Due to this, the average becomes 1 less than the previous one. What was the difference of the two digits p and q?

AQuA-RAT — Algebra Question Answering with Rationales (Ling et al., DeepMind, 2017) · train #34192