Praxis Core Academic Skills for Educators: Mathematics (5733)Number and QuantityMedium
A city planner is calculating the population density of a new development. The development covers an area of 4 square miles and has a population of 25,000 residents. What is the population density in residents per square mile?
- A10,000 residents/sq mi
- B100,000 residents/sq mi
- C25,000 residents/sq mi
- D6,250 residents/sq mi
Show answer & explanationAnswer & explanation
Correct answer: D. 6,250 residents/sq mi
Population density is calculated by dividing the total population by the total area. So, 25,000 residents / 4 square miles = 6,250 residents/square mile.
Why the other options are wrong
- A. This would be the result if the population was 40,000.
- B. This would be the result if population was multiplied by area, or if the population was 400,000.
- C. This would be the result if the area was 1 square mile.
Unit Rate Calculation
A unit rate expresses how much of one quantity there is per one unit of another quantity. It is typically calculated by dividing the total amount of the first quantity by the total amount of the second quantity.
- Unit rates simplify comparisons between different situations.
- Common unit rates include miles per hour, cost per item, and residents per square mile.
- The word 'per' often indicates division.
Memory trick: Divide total quantity by total units to get 'per one'.