Playing the piano taught me math (2016)

While we only have 10 fingers, there are many more keys on the piano on which the fingers can be place. Fiddling with my fingers to add and subtract numbers, I discovered a system of "Number fingering" such that I can consistently use my fingers to derive results of addition and subtraction. To find "4 + 2", you would start the left index finger and all fingers to the left pressed down on the table, then tap down the next two fingers to the right. Start with the right middle finger and all the fingers to the left of it pressed down on the table. After lifting 3 fingers one at a time from the right to left, the numerical decoding of the next finger to the left is "5". Specifically, fingers are lifted off the table from right to left for subtraction whereas fingers are pressed down from left to right for addition. Our ancestors must have counted with their fingers because it cannot be just a coincidence that we have 10 fingers and we use the decimal system.