I need to find three positive integers that add up to 72 and have a ratio of 1:3:4. Let me call the smallest integer x, then the other two are 3x and 4x. So I have x + 3x + 4x = 72. Simplifying, I get 8x = 72. Dividing by 8, I get x = 9. So the smallest integer is 9, and the other two are 27 and 36. 
Three positive integers have a sum of 72 and are in the ratio 1:3:4. What is the least of these three integers?