Mental Floss

Brain Game: Apollo's Friday

By BY
facebooktwitterreddit

It's Free-for-All Friday here at the mentalfloss.com Brain Game. And to allay your suspicions, there's no fooling in today's game, except for the title. Good luck!

Can  you quickly tell which of these five numbers is evenly divisible by 3? If so, how? 8 62 353 2120 50,631

Here is the SOLUTION.

THE SOLUTION:

50,631

To tell if any whole number is evenly divisible by three, add together the individual digits of that number. If the solution is evenly divisible by three, then so is the number:

8 = 8 (not evenly divisible by 3)
6 + 2 = 8 (not evenly divisible by 3)
3 + 5 + 3 = 11 (not evenly divisible by 3)
2 + 1 + 2 + 0 = 5 (not evenly divisible by 3)
5 + 0 + 6 + 3 + 1 = 15 (this one IS evenly divisible by 3)

Do you have a different "shortcut" way of telling if a number is divisible by 3? If so, please share it with us in the comments. And have a great weekend!

facebooktwitterreddit