This calculator doesn’t show you the answer until you first enter a suitable estimate. It’s like it says: “OK, I’ll calculate it for you but I want to check if you are still being human and still don’t forget to use your brain.”
I think it is a wonderful idea for writing computational software for science, engineering, and finance.
If our programs only give answers in response to inputs, we risk to get wrong results. Especially if we start trusting a software more than it deserves to be trusted.
This is often the situation with statistical calculations. People put their data into some cool package like SPSS, get nonsense out of it, and then report it in publications with some weird conclusions.
This also happens in many fields of science these days because modern data are huge and software packages are plentiful.
Technology is supposed to help us but if we allow ourselves to depend on it too much and switch off our brains while using the technology, then we are in trouble.
We need software that while giving us results makes occasional tests that we still know what we are doing.
Qama calculator is a good example. Want to get the answer? First give a rough guess. If your guess is reasonable, then it’s OK, you are thinking in the right direction, here is the exact answer for you.
If, however, your guess is crazy, then something is wrong with you. You are probably entering wrong numbers or pushing wrong buttons.