Ask your spectator to mix up all the blocks in their hands and then lie them on a table next to each other vertically. The spectator can lie them on the table in any colour order they wish.
Now for the maths magic! Tell the spectator to read the lines of numbers horizontally and then add up all the lines. For instance in the picture below you will see the numbers read across 4967, 9342, 7726 and 5689. Let's presume for learning purposes that this is the combination that the spectator chose. They would need to add up all of these combinations.
Usually a person would need to use a calculator or require some serious time to add up the big numbers. But you will know like magic and SUPER FAST! It's easy to solve the mystery and wow your audience with a simple formula.
Take a look at the third row of numbers in the picture above. The third row of numbers will always tell you the secret! The third line is 7726 in the example picture above. Always deduct (minus) two from that number (which will be 7724) and then place the 2 in front of all the numbers. The correct answer will be 27724! You will be able to reveal the answer to any combination in seconds!
People will think you are a magic mathematician!