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Universal Speed Rules

Universal Speed Rules

SituationFastest move
Percent or ratio problemConvert to fraction if clean: 12.5% = 1/8, 16.67% = 1/6
Change from old to newAlways divide by original value
"By what percent is A more than B?"(A - B) / B * 100
"By what percent is A less than B?"(B - A) / B * 100
Options are far apartApproximate first, calculate only if close
Big numbersFactor, cancel, or use percentages before multiplying
Word problemWrite only variables needed for answer
GeometryDraw a clean diagram and mark equal angles/lengths
Number systemPrime factorize first when divisibility, factors, LCM/HCF appear
Counting/probabilityCount total cases first, then favorable cases

High-ROI fraction to percent table:

FractionPercentFractionPercent
1/250%1/812.5%
1/333.33%3/837.5%
2/366.67%5/862.5%
1/425%7/887.5%
3/475%1/911.11%
1/520%2/922.22%
2/540%1/119.09%
3/560%1/128.33%
4/580%1/166.25%
1/616.67%1/205%