How many four digit numbers are there with distinct digits?

Question

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 $=10 \times 9 \times 8 \times 6=4320$.

Answer 1

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 $9 \times 9 \times 8 \times 7$.