Ratios and Proportions Worksheets – Grade 8 (Hard)

1. A recipe calls for 3 cups of flour for every 2 cups of sugar. If a baker wants to make a batch using 7.5 cups of flour, how many cups of sugar are needed?

2. Two similar triangles have corresponding sides in the ratio 5:8. If the smaller triangle has a perimeter of 45 cm, what is the perimeter of the larger triangle?

3. In a bag of colored marbles, the ratio of red to blue to green marbles is 4:7:9. If there are 36 green marbles, how many marbles are there in total?

4. A car travels 240 miles using 8 gallons of gasoline. At this rate, how many gallons would be needed to travel 390 miles?

5. The ratio of boys to girls in a math class is 3:5. If there are 12 boys in the class, how many students are in the class altogether?

6. A map scale shows that 2.5 inches represents 15 miles. How many miles would be represented by 7 inches on this map?

7. A mixture requires water and cement in the ratio 3:7 by weight. If 42 pounds of cement are used, how many pounds of water are needed?

8. Three business partners invest money in the ratio 2:3:5. If the smallest investment is $1,800, what is the total amount invested by all three partners?