Course Outline
Math Progress
0%
📊 Problem Solving~15% of SAT Math
Percentages & Percent Change
Calculate percentages, percent increase/decrease, and applications.
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Worked Example
Practice Problems
Problem
50
Problem
$100, +20%, then -20%
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SAT Strategies
Pro Tips & Shortcuts
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SAT Tip: Memorize common percent-decimal-fraction equivalents for speed.
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SAT Tip: The word "of" in percent problems means multiply.
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SAT Tip: Common mistake: dividing by the new value instead of the old value.
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SAT Tip: Always divide by the original value, not the new value.
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SAT Tip: Successive percent changes don't cancel! The base changes after each step.
⚡ Shortcut
10% = 0.1, 20% = 0.2, 33⅓% = 1/3, 66⅔% = 2/3
⚡ Shortcut
Quick mental math: 10% = divide by 10, 50% = divide by 2, 25% = divide by 4.
⚡ Shortcut
Difference over original: find the change, divide by where you started.
⚡ Shortcut
10/40 = 1/4 = 0.25 = 25%
⚡ Shortcut
Multiply by (1 + rate) for increase, (1 - rate) for decrease.