Percentage Benchmarks (50%, 25%, 10%, 1%)

Mental Math · Axiom Academy

LESSON Percentage Benchmarks (10%, 25%, 50%) Master the key percentage benchmarks for lightning-fast mental calculations 1. The 10% Benchmark: Just Move the Decimal Finding 10% of any number is incredibly simple: just move the decimal point one place to the left . This works because 10% means "10 out of 100" or dividing by 10. 10% of 80 = 8 (move decimal: 80.0 → 8.0) 10% of 250 = 25 (move decimal: 250.0 → 25.0) 10% of 47.50 = 4.75 (move decimal: 47.50 → 4.750) Real-World Use: Calculating a quick tip at a restaurant? 10% is your starting point. For a 42 meal, 10% = 4.20. Want to tip 20%? Just double it to 8.40! 2. The 50% Benchmark: Just Cut It in Half Finding 50% is even easier: divide by 2 . Since 50% means "half," this benchmark is perfect for quick mental math. Halving is one of the most natural operations our brains perform. Real-World Use: Huge sale at the store? "50% OFF" means you pay half price. If a jacket costs 80, you'll pay 40. If shoes are 65, you'll pay 32.50. 3. The 25% Benchmark: Half of Half Finding 25% builds on what you already know: divide by 4, or take half of 50% . Since 25% is one quarter, and you already know how to find half, this is just one extra step! 25% of 80 = 20 (Half of 50% → Half of 40 → 20) 25% of 200 = 50 (200 ÷ 4, or half of 100) Real-World Use: "25% OFF" sales are common. For a 60 item, find 50% ( 30), then halve it to get 15 off. You pay 45. Or, you can think: 60 ÷ 4 = 15 off.

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