# How many four digit numbers are there with distinct digits?

I am confused with two methods, which one is correct?

1. If we start from the thousands place, total number of such numbers $$=9 \times9 \times 8 \times 7=4536$$.
2. If we start from the units place, total number of such numbers $$=10 \times 9 \times 8 \times 6=4320$$.
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Another way: if you consider all four-digit numbers with no repeated digits (including the ones that start with 0), there are $$10 \times 9 \times 8 \times 7$$ of them. Now count the four-digit numbers whose first digit is 0 and which have no repeated digits: there are $$9 \times 8 \times 7$$ of them. Subtracting, we get $$9 \times 9 \times 8 \times 7$$.