NumberThink is a learning aid for the Major System, which is a well-known technique for remembering numbers by associating them with words.

In the Major System, each digit of a number is associated with a sound (not a letter). By combining the sounds to form words, you just need to remember the words to remember the number.

Some letters are not associated with numbers (a, e, i, o, u and w) so these letters can be added as needed.

For example, if you want to remember the number 91, you could simply remember the word "bat", since "b" is associated with 9 and "t" is associated with 1, and "a" isn't associated with a number. You could also remember the word "bet" since "e" is also not associated with a number.

NumberThink helps you learn the Major System in two ways:

1. To help you learn how to form words from numbers, you can enter a number and touch the ! button to have NumberThink think of a word that is associated with that number.

2. To help you learn how to figure out the number associated with a word, you can press the # button (or shake the app) and it will think of a word that you have to enter the number for.

A common use of the Major System is to use it to create a set of specific "peg" words for all the numbers from 1 to 100 (or higher). This can make it easier to build a phrase for particular number since you always use the same set of peg words.

You can customize the peg words by editing the built-in ones or adding your own. You can copy your word list from one iPhone or iPad to another using iTunes. Just go to iTunes > Apps > File Sharing and copy the "numberthink.sql" file to your desktop and then copy it into another device via iTunes.