If a number is divisible by 12,18,30. Then it should be a multiple of LCM of 12,15 and 18 . Now, LCM of 12,15 and 18=2×2×3×3×5=180 The smallest 5 -digits number is 10000 . Now, divide it by 180. We get a quotient 55 remainder is 100 . If we add 80 to it then it will be completely divided by 180 with a quotient 56. Therefore, 180*56=10080