Apply ratios, proportions, rates, and percent change in context.
Decide whether the situation calls for a ratio, rate, proportion, or percent change.
核心知识
Identify which two quantities are being compared, keep the units attached, and decide whether the situation asks for a ratio, a unit rate, a proportion, or a percent change.
深入理解
Rule: These problems are usually straightforward once you label the comparison correctly.
Ratios compare part to part or part to whole, proportions set equivalent ratios equal, rates describe one quantity per unit of another, and percent change compares the change to the original amount, not the new amount. On ACT questions, many mistakes come from using the right numbers in the wrong order or dropping the units too early.
示例解析
A concert ticket price increased from
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