An intelligence agency forms a code of two distinct digits selected from…

An intelligence agency forms a code of two distinct digits selected from 0, 1, 2, …, 9 such that the first digit of the code is nonzero. The code, handwritten on a slip, can however potentially create confusion when read upside down — for example, the code 91 may appear as 16. How many codes are there for which no such confusion can arise?

AQuA-RAT — Algebra Question Answering with Rationales (Ling et al., DeepMind, 2017) · train #23490