快速计算 X% of Y、百分比增减、占比
Quickly calculate X% of Y, percentage change, and more
Divide the part by the whole and multiply by 100. For example, if you scored 45 out of 60: (45 ÷ 60) × 100 = 75%.用部分除以整体再乘以 100。例如考了 45 分（满分 60）：(45 ÷ 60) × 100 = 75%。
Multiply Y by X and divide by 100. For example, 25% of 200 = (200 × 25) ÷ 100 = 50.用 Y 乘以 X 再除以 100。例如 200 的 25% = (200 × 25) ÷ 100 = 50。
Subtract the old value from the new, divide by the old value, multiply by 100. Formula: ((New − Old) ÷ Old) × 100.新值减去旧值，除以旧值，乘以 100。公式：((新 − 旧) ÷ 旧) × 100。
Same formula as increase. A result of −20% means a 20% decrease from the original value.和增长公式相同。结果为 −20% 表示比原值降低了 20%。
A percentage is a ratio out of 100. A percentile indicates your position in a ranked group — e.g., 90th percentile means you scored higher than 90% of people.百分比是 100 为基数的比率。百分位表示你在排名中的位置——如第 90 百分位意味着你超过了 90% 的人。