Marking (/) those which are are divisible by 3 by not by 9 and the others by (X), by taking the sum of digits, we get:s
2133
9 (X)
2343
12 (/)
3474
18 (X)
4131
9 (X)
5286
21 (/)
5340
12 (/)
6336
18 (X)
7347
21 (/)
8115
15 (/)
9276
24 (/)
Required number of numbers = 6.
