I'm trying to do this exercise and I'm stuck at 3 and 4 part. Is there any website or some youtube video can someone recommend to me, so I can understand how to do this kind of questions. With question three should I take the largest number and the smallest and subtract them to get an answer? Thanks.
The digits 0,2,4,6,8 are used to form four-digit codes. A code cannot begin with 0 and no digit is repeated in any code.
i) Write down the largest possible four digit code. ii) Write down the smallest possible four digit code. iii) How many four digit codes can be formed. iv) How many of the four digit codes are greater than 4000.
My answer: i) 8642 ii)2046