1 votes 1 votes Number of 5 digit number having there digits in non decreasing order (from left to right) constructed by using the digits belonging to the set {1, 2, 3, 4, 5, 6, 7, 8, 9} ? Combinatory discrete-mathematics combinatory + – Shubhanshu asked Apr 28, 2017 retagged Jun 27, 2017 by Arjun Shubhanshu 664 views answer comment Share Follow See all 2 Comments See all 2 2 Comments reply Nirmal Gaur commented Apr 28, 2017 reply Follow Share it is a finite set, repetition is not possible 0 votes 0 votes Shubhanshu commented Apr 28, 2017 reply Follow Share Repetition is possible because it is not said that its digits are in increasing order. here it is non-decreasing order hence repetition is allowed. 0 votes 0 votes Please log in or register to add a comment.
2 votes 2 votes 5 digit no. with non decreasing order is same as selecting five digit and after selection we can arrange that 5 digit only in one way. if repetition is not allowed we can select in 9c5. and if repetition is allowed then we can select in 13c5. ANKUSH KUMAR answered Apr 28, 2017 ANKUSH KUMAR comment Share Follow See all 7 Comments See all 7 7 Comments reply Show 4 previous comments Shubhanshu commented Apr 29, 2017 reply Follow Share ok, I got it since in digit places we can place only one digit at a time. but in box and ball example we can put multiple balls at a time in a single box that's why it is calling as repetition and hence the number of boxes we have is 5 and objects as 9. but in our example, we have 9 boxes(digits from the set) and 5 balls(places in five-digit number). Through this, we can take the same digit for multiple places. ryt??? 0 votes 0 votes ANKUSH KUMAR commented Apr 29, 2017 reply Follow Share yes..u r ryt.. 0 votes 0 votes Shubhanshu commented Apr 29, 2017 reply Follow Share thanks .... 0 votes 0 votes Please log in or register to add a comment.