The ratio of three positive integers is 2:4:5 and their least common multiple is 300. What is the sum of the smallest and the largest of the three numbers?

Answer 1

If the numbers are LCM(2x,4x,5x) = 20x
So, x=15. But 5|15, so use x=3 and the numbers are

30,60,75

30+75 = 105