Find the largest number of four digits which is exactly divisible by 18,25 and 35
well, check the factors of each number.
18 = 2 * 3^2
25 = 5^2
35 = 5 * 7
So, LCM(18,25,35) = 2 * 3^2 * 5^2 * 7 = 3150
Now, how many multiples of 3150 have only four digits?