The Nine Barrels
In how many different ways may these nine barrels be arranged in three tiers of three so that no barrel shall have a smaller number than its own below it or to the right of it? The first correct arrangement that will occur to you is I 23 at the top, then 4 5 6 in the second row, and 789 at the bottom, and my sketch gives a second arrangement. How many are there altogether?
The answer is 42.
This section requires Javascript.
You are seeing this because something didn't load right. We suggest you, (a) try
refreshing the page, (b) enabling javascript if it is disabled on your browser and,
finally, (c)
loading the
non-javascript version of this page
. We're sorry about the hassle.
1 solution
