0 votes 0 votes How many ways 20 distinct numbers can be arranged in location/index 1 to 20 such that,three particular numbers(say 3,10,20) will always be present in the first half.(3,10,20 location/index will be always <11) ? Combinatory discrete-mathematics combinatory counting + – rahul sharma 5 asked Oct 29, 2017 rahul sharma 5 295 views answer comment Share Follow See all 3 Comments See all 3 3 Comments reply akb1115 commented Oct 29, 2017 reply Follow Share 10C3 *3! *17! ??? 1 votes 1 votes Rishabh Gupta 2 commented Oct 29, 2017 reply Follow Share First we will select 3 positions for three chosen numbers (3, 10, 20), = 10C3 * 3! Then 17! for permutating remaining elements. Total = 10C3 * 3! *17! I am not sure. What do u think? 1 votes 1 votes rahul sharma 5 commented Oct 29, 2017 reply Follow Share Correct.Thanks 1 votes 1 votes Please log in or register to add a comment.