Twitter Challenge

  We retweeted this here: https://twitter.com/centerofmath

This twitter post by English computer programmer Paul Graham is generating a lot of buzz. Graham gave us a little more information in his next tweet; apparently the problem was taken from a UK exam aimed at 11 and 12 year old children. We at the Center of Math decided to solve the problem for ourselves. Here's how I worked out this simple, yet deceiving, pattern problem:

Click the picture to make it larger!

I solved the problem by looking for a pattern in the difference between each number:

• Add 1 to the initial value of 16 to get 17, and add 1 to get 18. These two lines make the first A and B set.
• Add 0 to 18 for the next 18 value, and then add 2 to get 20. This is my second A, B set.
• Then, add negative 1 to 20 to get 19. Add 3 to 19 to get 22, the final answer. This resulted in another A, B set.
• (Extra step: continue on for a few more lines to see where the numbers lead.)

Did you solve this problem a different way? What are your thoughts on the level of difficulty? Should this be a problem for 11 and 12 year olds? Let us know in the comments!

-Tori