Mental Math Quiz: No Calculator Allowed
Percentages, tips, change and estimates — the arithmetic of real life, against your own brain only.
About this quiz
Put the phone calculator away. These ten questions are the arithmetic of American daily life: a 20% tip, a 30%-off jacket, whether the big box is really cheaper per ounce, and what 15% of your paycheck looks like. Each has a clean mental path — find it, and notice the trick for next time (the explanations ride along with the answers).
Frequently Asked Questions
What is the trick to mental percentages?
Build from 10%: 10% of anything is a decimal shift. 20% is double that, 5% is half, 15% is 10% + 5%. Most real-life percentages assemble from those pieces.
What is a good score?
7+ means your mental arithmetic is sharper than most. These are the exact calculations that decide tips, sales and budgets every week.
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