Permutations and Combinations Part 2

For number to be divisible by 15 , last digit should be 5 and sum of digits must be divisible by 3 .
Possible combinations are

1

2

1

5

Numbers =3

2

2

3

5

Numbers =3

3

3

1

5

Numbers =3

1

1

5

5

Numbers =3

2

3

5

5

Numbers =3

3

3

5

5

Total Numbers =21