If digits are not to be used with repetition, find the number of four- digit odd numbers divisible by 15 which can be formed by using 0,2,3,5,6,7, and 9?

Question

Answer: 30
The answer is 30, but I don't know how to get 30, please help me how to solve it🙏

Answer 1

divisible by 15 means divisible by 5 and by 3
... the number must end in 5 (an odd number)
... if a number is divisible by 3, the sum of its digits is divisible by 3

so the three digits before the five must sum to
... 10 or 13 or 16 or 19 or 22
... the digits can be in any order

307 , 370 , 703 , 730

etc.

Answer 2

I still don't understand🙏 why must sum to 10 or 13 or 16 etc.?
Can we use combination to solve it?