How many 6 digit numbers can be made using digits 1 , 2 , 3 , 4 , 5 , and 6 without repetition such that the hundred digit is greater than the ten digit , and the ten is greater than the one digit ?
How many 4 digit numbers can be formed by using 0 , 1 , 2 , 3 , 4 , 5 , 6 , and 7 ? How many of them are between 4000 and 6000 ?