Part-over-whole, percent change, reverse percentages, and compound patterns broken down clearly.
Absolute error divided by accepted value times 100—lab reports require consistent significant figures when rounding.
Two 10% increases do not equal 20% total—multiply growth factors (1.10 times 1.10) instead of adding percents.
Markup is percent of cost; margin is percent of selling price—same dollars, different denominators, different percentages.
Always divide change by the original value before increase or decrease—swapping base inflates or shrinks reported change.
Percentage equals part divided by whole times 100—the whole must be the reference set, not the larger number by habit.