Praxis Core Academic Skills for Educators: Mathematics (5733)Number and QuantityMedium
A landscaper is mixing soil for a new plant bed. He uses 3 parts topsoil, 2 parts compost, and 1 part sand. If he needs a total of 18 cubic feet of soil mix, how many cubic feet of compost will he need?
- A12 cubic feet
- B6 cubic feet
- C3 cubic feet
- D9 cubic feet
Show answer & explanationAnswer & explanation
Correct answer: B. 6 cubic feet
First, find the total number of 'parts' in the mix. Then, determine what fraction of the total mix is compost and apply that fraction to the total required volume.
Why the other options are wrong
- A. This would be if compost was 2/3 of the mix, which is incorrect.
- C. This is the amount of sand (1 part).
- D. This is the amount of topsoil (3 parts).
Ratio and Total Quantity
When given a ratio of parts and a total quantity, you can determine the amount of each individual part by finding the fraction each part represents of the total parts.
- Sum the ratio parts to find the 'total parts'.
- Each component's amount is (component's part / total parts) * total quantity.
- Ensures the proportions are maintained for any total quantity.
Memory trick: Ratio Parts Make Total Parts!