The answer would be 1800 possible 4 digit numbers. In the thousands place, there are 9 possible digits (1,2,3,4,5,6,7,8,9), in the hundreds place, there are 10 possible digits (1,2,3,4,5,6,7,8,9,0), in the tens place, there are 10 possible digits (1,2,3,4,5,6,7,8,9,0), and in the ones digit, there are 2 possible digits (0,5). This is because it is a multiple of 5, which means it ends in either a 5 or a zero. Then, you multiply the number of possible digits in each place (9*10*10*2) which equals 1800.