If 4 equally productive workers finish a task in 10 days, how many worker-days does it require?

Question: If 4 equally productive workers finish a task in 10 days, how many worker-days does it require?

1. 40 worker-days
2. 41 worker-days
3. 39 worker-days
4. 42 worker-days

Correct Answer: A — 40 worker-days

Explanation: Worker-days = number of equal-rate workers × days worked.
Using the values in this question gives 40 worker-days as the correct answer.