24, of which 6 will begin with zero. Excluding these, gives 18.
∞ \ Infinite
There are 192.
Ten different digits can be used to make 10C4 = 10*9*8*7/(4*3*2*1) = 210 four-digit numbers. Either numbers starting with 0 are permitted or the 10 digits do not contain a 0.
Without repeating digits (not digets!) and without leading 0s, 600 of them.
162
∞ \ Infinite
There are 192.
2*3*3*3*3 = 162
Ten different digits can be used to make 10C4 = 10*9*8*7/(4*3*2*1) = 210 four-digit numbers. Either numbers starting with 0 are permitted or the 10 digits do not contain a 0.
Without repeating digits (not digets!) and without leading 0s, 600 of them.
1x+4y=
162
The are 100,000,000.
Any pair of digits (not including 0), can be used to generate 14 four-digit numbers. If one of the digits is 0, only seven will start with a non-zero digit.
There are 900 of them.
95
100000 - including numbers with leading 0s