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Shortcut used: Convert each person's time into one-day work, then add or subtract work rates.
Solve in 3 steps:
- Take total work as 1 or LCM.
- Find each one-day work rate.
- Combine rates as required.
Common mistake: Do not add days directly when people work together.
Question 2
Multiple Choice Question
Question
A completes a job in 20 days and B in 30 days. Working together, how many days do they need?
Explanation
Correct Answer: B
ANSWER
Correct Answer: B
Method / Topic: Time and Work
Combined rate = 1/20+1/30 = 1/12. Time = 12 days.
Why this answer is correct
The answer is based on combined work rates.
Short Explanation
Combined rate = 1/20+1/30 = 1/12. Time = 12 days.
Detailed Explanation
Question
A completes a job in 20 days and B in 30 days. Working together, how many days do they need?
ANSWER
Correct Answer: B
Method / Topic: Time and Work
The rates add to five-sixtieths, which simplifies to one-twelfth.
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Question 2
Learn + Solve: Shortcut, Trap & Fast Route Click to view shortcut, steps, and common mistake
Learn + solve
Shortcut used, common trap, and the fastest solving route
Shortcut used: Convert each person's time into one-day work, then add or subtract work rates.
Solve in 3 steps:
- Take total work as 1 or LCM.
- Find each one-day work rate.
- Combine rates as required.
Common mistake: Do not add days directly when people work together.
Question
A completes a job in 20 days and B in 30 days. Working together, how many days do they need?
Explanation
Correct Answer: B
ANSWER
Correct Answer: B
Method / Topic: Time and Work
Combined rate = 1/20+1/30 = 1/12. Time = 12 days.
Why this answer is correct
The answer is based on combined work rates.
Short Explanation
Combined rate = 1/20+1/30 = 1/12. Time = 12 days.
Detailed Explanation
Question
A completes a job in 20 days and B in 30 days. Working together, how many days do they need?
ANSWER
Correct Answer: B
Method / Topic: Time and Work
The rates add to five-sixtieths, which simplifies to one-twelfth.
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