This is just a slightly-gamified version of mental arithmetic training flashcards. Are you questioning why mental arithmetic is useful? There are lots of places

This is just a slightly-gamified version of mental arithmetic training flashcards. Are you questioning why mental arithmetic is useful? There are lots of places where it can improve your ability to understand the information around you. If you're reading a graph, you should be asking yourself a ton of questions about it. A lot of those questions can be answered with mental math if you're proficient at it. If you weren't, you'd have to resort to a calculator or other tool, and the switching cost keeps most people from doing this: examples: what's the ratio between these two values? How did it change? I have this per minute (or, in my case, a per 4 minutes) rate. What is that per day? How much did that drop by (absolute and relative) The point isn't that people who are bad at math can't compute these things in the real world. They can, and often do, whether with calculator, on paper, slower in their brains, or with a different query or better analysis tool. But people who do these operations quickly mentally do it more, do it more quickly, and can digest and filter more numeric information.