5 votes 5 votes How many strings of $5$ digits have the property that the sum of their digits is $7$? $66$ $330$ $495$ $99$ Combinatory ugcnetcse-june2015-paper2 discrete-mathematics counting + – go_editor asked Jul 30, 2016 edited Jun 5, 2020 by go_editor go_editor 2.8k views answer comment Share Follow See all 0 reply Please log in or register to add a comment.
Best answer 6 votes 6 votes Let five digit A, B, C, D, E then A + B + C + D + E = 7 given n = 7, r = 5 we know that n + r – 1 C r - 1 = 7+5 -1 C 5-1 = 11 C 4 = 11x 10x9x8/1x2x3x4 =330 Answer B sh!va answered Jul 30, 2016 selected Jul 30, 2016 by srestha sh!va comment Share Follow See all 3 Comments See all 3 3 Comments reply VASUGANESHAN commented Jul 2, 2018 reply Follow Share Let five digit A, B, C, D, E then A + B + C + D + E = 7 If A is 0 then it won't be 5 digit string.So, we consider this too.. Tell me if I am wrong.. 1 votes 1 votes anchitjindal07 commented Aug 3, 2018 reply Follow Share It's saying "strings", not numbers... I think that's the catch 3 votes 3 votes keshav777 commented Oct 22, 2020 reply Follow Share can someone give context for the formula used here. how is it used?’ 0 votes 0 votes Please log in or register to add a comment.
0 votes 0 votes This simple star-bar problem with IODB template where the a+b+c+d+e=7 which is equivalent to Combination with repitition, where content does not matters only order matters. THere are 7 stars and 4 bars. (7+4)C4==330 Vasudevarnabmessi answered Jul 21, 2022 Vasudevarnabmessi comment Share Follow See all 0 reply Please log in or register to add a comment.