Einstein's Favorite Number Trick!

Einstein was fascinated with numbers and loved using his superior math skills to stump his friends!

Today we learned about one of those tricks -- the Mysterious Number 1089...

Go ahead and try out the trick below on your friends and family:

1. take a piece of paper and write down the number 1089, fold the paper in half, and give it to the other person, without revealing what you have written.

2. Tell the person to pick any three-digit number in descending order, making sure that the first and last digit differ by at least 2

3. Tell this person to reverse the digits and to subtract the smaller number from the larger number.

4. Then have this person take the result of the subtraction, and add it to the result with the numbers in reverse.

5. Then ask this someone to compare the final result with the number you wrote on the piece of paper at the start.

Let’s run through this with an example. Suppose your friend picks 523. This number is acceptable since 5 and 3, the first and last digits, differ by 2. Now reverse this to get 325 and subtract this from 523. Now 523-325 = 198. Reverse 198 to get 891and add to 198 to get 1089!

Try it out yourself -- with any three digit number that contains descending values. Can you find a situation where it doesn't work?

Can you figure out why the trick works? That is the challenge for this week -- to try and figure out how this trick works -- but you are going to have to do some algebra to figure it out!