To find the number of 7 digit odd number formed by using the seven digits 1,2,2,2,3,3,5
We will take following cases,
Case 1− fixing 1 as unit place,
So total number of ways will be 3!2!6!as 2is repeating three times and 3 is repeating two times
Case 2− fixing 3 unit place,
So total number of ways will be 3!6!
Case 3− fixing 5 as unit place,
So total number of ways will be 3!2!6!
Now adding all the cases we will get, total number of ways as 3!2!6!+3!6!+3!2!6!=60+120+60=240