determine the smallest 6 digit number which is exactly divisible by 8,15,and21

Find the least common multiple of 8, 15, and 21. . . . . . It's 280 .So all the numbers divisible by 8, 15, and 21 are all the multiples of 280.The smallest 6-digit number is 100,000 .100,000 / 280 = 357.1 , so the next whole-number multiple is the 358th one.280 x 358 = 100,240 .You can tell right away that this is the smallest one that qualifies, because if you take away 280 and go to the next smaller multiple,it won't have 6 digits anymore.