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Twist your brain
A good puzzle answer starts with asking the right question, not calculating quickly. In Twist your brain you examine ratios, conditions and hidden assumptions. You enter your own answer and then see the reasoning. Even a wrong answer can show you which step was missing.
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How it works
Read the whole question and check the units. Enter a number, fraction or short answer as requested. Both a decimal point and a decimal comma are accepted. After a wrong answer you can try again; the hint points you in a direction without giving away the full solution.
Worked example
A backpack costs €50. You get 10% off, then another 10% off the new price. You pay €50 × 0.90 × 0.90 = €40.50, not €40. Two percentage changes apply to different amounts. Writing down the intermediate price prevents this common mistake.
A useful approach
Easy uses short calculations and concrete riddles. Medium usually needs several steps. Hard may combine probability or combinations with extra conditions. Check your result by putting it back into the question: do the amount, time and ratio still fit all the information?