Ratios and Proportions Flashcards

A recipe calls for 2 cups of flour for every 3 cups of oats. If you use 8 cups of flour, how many cups of oats do you need?

Answer: 12 cups

Set up the proportion 2/3 = 8/x, then cross-multiply to get x = 12.

A map uses a scale of 1 inch = 50 miles. If two cities are 3.5 inches apart on the map, what is the actual distance?

Answer: 175 miles

Multiply 3.5 inches by 50 miles per inch to get 175 miles.

The ratio of boys to girls in a class is 4:5. If there are 20 boys, how many girls are there?

Answer: 25 girls

Set up 4/5 = 20/x and solve: x = (20 × 5) / 4 = 25.

If 5 pounds of apples cost $7.50, how much do 8 pounds cost?

Answer: $12.00

The unit price is $1.50/lb, so 8 × $1.50 = $12.00.

Which ratio is NOT equivalent to 6:9?

Answer: 3:5

6:9 simplifies to 2:3; 3:5 does not equal 2:3.

A car travels 180 miles in 3 hours. At the same speed, how long will it take to travel 270 miles?

Answer: 4.5 hours

Speed = 60 mph; 270 ÷ 60 = 4.5 hours.

A store mixes coffee beans in a ratio of 3 parts dark roast to 2 parts light roast. How many pounds of dark roast are needed to make a 25-pound blend?

Answer: 15 pounds

Dark roast is 3/5 of the total: (3/5) × 25 = 15 pounds.