Fractions, decimals, and percents; percent change — ISEE Upper practice questions

Common decimals are worth knowing as fractions; for example, three-eighths equals point three seven five. Percent change is always measured from the original amount: a rise from forty to fifty is a twenty-five percent increase, but a fall from fifty to forty is only a twenty percent decrease.

Multi-step problems apply successive increases and decreases, and the clean way to undo them is to divide by each multiplier rather than subtract percents. Choices often include the answer reached by simply adding the percents, so checking the result against the wording is worthwhile.