Ratios and Proportions
Ratios and proportions are essential topics in the SAT Math section. You’ll need to solve problems that involve setting up proportions and solving for unknowns.
Example:
If the ratio of boys to girls in a class is 3:5, and there are 24 boys, how many girls are there?
If the ratio of boys to girls in a class is 3:5, and there are 24 boys, how many girls are there?
Step 1: Set up the proportion:
3/5 = 24/x
Where x is the number of girls.
Step 2: Cross-multiply:
3x = 5 × 24 = 120
Step 3: Solve for x:
x = 120/3 = 40
Answer: There are 40 girls in the class.
Percent Problems
Percent problems are common on the SAT, and they often ask you to find percentages of numbers or solve for the original value when given a percent change.
Example:
A store is having a 25% off sale on a jacket originally priced at $80. What is the sale price?
A store is having a 25% off sale on a jacket originally priced at $80. What is the sale price?
Step 1: Find 25% of $80:
0.25 × 80 = 20
Step 2: Subtract $20 from the original price:
80 – 20 = 60
Answer: The sale price is $60.