SET 12 – TEAS 7 Math: Ratios, Proportions, & Percentages

Ratio

Comparison of two quantities

Proportion

Equation showing two ratios are equal

Solve proportion

Cross multiply and divide

Rate

Ratio comparing different units

Unit rate

Rate per 1 unit

Percent

Out of 100

Percent to decimal

Move decimal left two places

Decimal to percent

Move decimal right two places

Fraction to percent

Divide numerator by denominator, then ×100

Percent to fraction

Write over 100 and simplify

Percentage formula

Part = Whole × Percent

Find part

Whole × Percent

Find whole

Part ÷ Percent

Find percent

Part ÷ Whole

Percent increase

(New − Old) ÷ Old × 100

Percent decrease

(Old − New) ÷ Old × 100

Markup

Cost × Percent added

Markdown

Original price × Percent decreased

Sales tax

Price × Tax rate

Discounted price

Original price − Discount

Final price with tax

Price + (Price × Tax)

Simple interest

I = P × R × T

Principal

Starting amount of money

Rate

Interest percentage

Time

Duration money is borrowed

Mixture problem

Combine amounts using weighted averages

Proportion setup

a/b = c/d

Scale factor

Ratio used to enlarge or shrink

Direct variation

y increases as x increases

Inverse variation

y increases as x decreases

Solve direct variation

y = kx

Solve inverse variation

y = k/x

Probability

Favorable ÷ Total outcomes

Odds

Favorable : Unfavorable

Change percent to multiplier

20% increase = ×1.20

Decrease percent to multiplier

20% decrease = ×0.80

Convert ratio to fraction

a:b = a/b

Convert fraction to ratio

a/b = a:b

Proportion word clue “is to”

Means use a ratio

Proportion clue “out of”

Represents a fraction

Percent clue “of”

Multiply

Percent clue “what”

Indicates unknown value

Successive percent changes

Apply multipliers sequentially

Increase followed by decrease

Does not return to original

Decrease followed by increase

Does not return to original

TEAS trap: Percent change uses old value

Always old value in denominator

TEAS trap: Cross multiply only works with proportion

Must be ratio = ratio

TEAS trap: 50% off then 50% off again

Not free; becomes 25% of original

TEAS trap: Percent of a percent

Multiply the percentages