If 4 men in 5 days eat 7 pounds of bread, how much will be sufficient for 16 men in 15 days?

This math puzzle is said to have been a part of Abraham Lincoln's math homework during his teenage years. According to historians, Lincoln was able to get the correct answer of 84 pounds. How he got there is a bit of a mystery, but in modern mathematics, the best way to figure it out is to set it up as a proportion. Take 4 men * 5 days to get 20 man-days. Then you take 16 men * 15 days to get 240 man-days. From there, you take the 240 man-days and multiply that by (7 pounds of bread/ 20 man-days). That gives you your total bread allotment of 84 pounds. That's a lot of bread!

Asked by Ben Jenkins · Last updated 3 years ago · 1.8K views · SOURCE