Check your case arithmetic.
Paste the working from a case you have just done — or type some now. Every equation gets recomputed and compared against what you said it equalled. No account, nothing to install, nothing sent anywhere: this runs entirely in your browser.
Write the way you would in an interview — labelled terms are fine
($500M revenue - $120M profit = $370M). Percentages, crore and lakh all work.
What this is, and what it is not
This page does one thing: it checks whether the arithmetic you wrote is internally
consistent. If you write 500 - 120 = 370, it tells you the answer is 380.
That is useful, and it is roughly a fifth of what happens in a real case.
The full case does the rest. It runs an actual interview, then checks every figure you quoted against the case's own answer key — not just against your other numbers — and tells you which of your claims were off, by how much, and where the error first entered your reasoning. That part needs a case with a fixed ground truth behind it, which is what the library is.