How To Win at Ant Racing
Joe and
Rita are ant friends. They love to race each other but always
tie, since they crawl at the exact same speed. One day, they
designed a race that one of them could actually win.
For this race, they both start at the bottom corner of a cuboid, then crawl as
fast as they can to reach a crumb at the opposite corner. The measurements of
their cuboids are as pictured:
If they both take the shortest possible route to reach their crumb,
who will reach their crumb first? (Don’t forget they’re ants, so
of course they can climb anywhere on the edges or surface of the
cuboid.) Think outside the box!
Solution
The key to solving this
problem is to come up with the length of each of their shortest
routes. The simplest way to find this shortest route is to
flatten the box. Once the box is flattened, it’s very easy to
find the shortest route between the ant and their crumb.
The
shortest route between two points is a straight line!
In Joe’s case, flattening the box is straightforward. Since it’s
a cube, it doesn’t matter which way you flatten it. If you
flatten the top front fold, you’ll see the following
rectangle:
Clearly, Joe’s fastest route will be a straight line to the
crumb. Using the pythagorean theorem (or graph paper and a good
ruler), you can determine that his shortest path is √45 inches,
or 6.71 inches.
Rita’s is slightly trickier to figure out, as there are three
possible ways that you could “unfold” her cuboid:
Again, the pythagorean theorem—or a very good ruler—will tell us
the diagonal of the second rectangle is the shortest at √41
inches, or 6.40 inches. So Rita will achieve this route if she
crawls on the left most (unseen surface) and then onto the top: