Brain Teasers
Four Consecutive Natural Numbers
The product of four consecutive natural numbers is 9???4, and we don't know what the ?s are. Find the largest number of the four.
Answer
The product of four consecutive natural numbers end with a 4, therefore none of them can end with 5 or 0, and their unit digits can be only 1, 2, 3, 4 or 6, 7, 8, 9.Since 20^4=160000 and 15^4=50625, they can only be 16 through 19, and we check that 16*17*18*19=93024.
Therefore, the largest number of the four is 19.
Hide Answer Show Answer
What Next?
View a Similar Brain Teaser...
If you become a registered user you can vote on this brain teaser, keep track of which ones you have seen, and even make your own.
Solve a Puzzle
Comments hidden to avoid spoilers.
Follow Braingle!