1.

An intelligence agency forms a code of two distinct digits selected from 0, 1, 2, ..., 9 such that the firstdigit of code is non-zero. The code, handwritten on a slip, can however potentially create confusion when read upside down, for examples the code 91 may appear as 16. How many codes are there for which nosuch confusion can arise?

Answer»

80
78
71
69

Answer :D


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