Let P be the set of seven digit numbers with sum of their digits equal to 11 . If the numbers in P are formed by using the digits 1,2 and 3 only, then the number of elements in the set (P ) is :

Step-by-step solution

(i) number of numbers created using 1111133= 7! 5!2! 21 (ii) number of numbers created using 1111223= 7! 4!2! 105 (iii) number of numbers created using 1112222= 7! 4!3! 35 Total =161