Difficulty: Easy
Correct Answer: 12 days
Explanation:
Introduction / Context:
This is a basic “helper” problem: compare the solo time of one worker to the combined time with a helper, then solve for the helper’s solo time via rate subtraction.
Given Data / Assumptions:
Concept / Approach:
Daughter’s rate = together rate − mother’s rate = 1/4 − 1/6. Daughter’s time = reciprocal of her rate.
Step-by-Step Solution:
Daughter rate = 1/4 − 1/6 = (3 − 2)/12 = 1/12 per day.Daughter alone time = 1 / (1/12) = 12 days.
Verification / Alternative check:
Check: 1/6 + 1/12 = 1/4; correct combined rate.
Why Other Options Are Wrong:
16, 10, 8, or 14 days do not match the calculated helper rate.
Common Pitfalls:
Subtracting times instead of rates; remember to subtract 1/6 from 1/4, not 6 from 4.
Final Answer:
12 days
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