(1+-%/100)
When a value increases or decreases by a percent, use the growth/decay factor to calculate the new value.
Use for increase (greater than)
Use for decrease (less than)
Many word problems involve percentage increases or decreases. Using the 1 ± %/100 formula avoids multiple steps and ensures accurate comparison with inequalities.
(1+-%/100)
When a quantity increases or decreases by a percent, use a multiplicative factor to calculate the new value.
Use for an increase
Use for a decrease
Many word problems involve percent changes in finance, population, or measurements. Using the 1 ± %/100 formula allows for quick, accurate calculation without multiple steps.
Means to multiply the %/100 times the number.
The phrase “% of” signals multiplication between the percent (as a decimal) and the number.
To convert a percent to a decimal, divide it by 100.
Many SAT problems involve percentages in word form. Converting the percent to a decimal and multiplying correctly is essential to avoid simple arithmetic mistakes, especially in multi-step problems.
Turn coefficient to percent form.
To express a decimal or coefficient as a percent, multiply it by 100 and add the percent symbol (%).
Percent questions often use coefficients in equations (like growth rates or slopes). Converting between decimal form and percent form helps interpret what a value means in context, especially in exponential or real-world problems.
Turn coefficient to decimal form.
Key Idea: Times (Multiplying Decimals)
When multiplying, a coefficient can be converted to decimal form and multiplied directly.
General Rule:
Convert fractions or percentages to decimals if needed.
Multiply the numbers as usual.
Keep track of decimal places in the product.
Why this matters for the SAT:
Decimal multiplication appears in algebra, word problems, and data interpretation.
Converting coefficients to decimal form can simplify calculations and reduce errors.
