Question:medium

P and Q can complete a job in 24 days working together. P can alone complete it in 32 days. Both of them worked together for 8 days and then P left. The number of days Q will take to complete the remaining job is:

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An alternative approach is using the "Total Work" unit method. Let Total Work be the LCM of 24 and 32, which is 96 units. Efficiency of (P+Q) = 96/24 = 4 units/day. Efficiency of P = 96/32 = 3 units/day. Efficiency of Q = 4 - 3 = 1 unit/day. Work done in 8 days = 4 units/day * 8 days = 32 units. Remaining work = 96 - 32 = 64 units. Time for Q to finish = Remaining work / Efficiency of Q = 64 / 1 = 64 days.
Updated On: Mar 26, 2026
  • 26 days
  • 30 days
  • 64 days
  • 60 days
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The Correct Option is C

Solution and Explanation

Step 1: Conceptual Foundation:
This problem falls under the category of work and time. The established method involves calculating the rate of work, defined as the proportion of a job completed per unit of time.
Rate of Work = \( \frac{1}{\text{Total Time to Complete Job}} \)

Step 2: Methodology Outline:
1. Determine the combined work rate of P and Q (\(R_{P+Q}\)).
2. Determine the individual work rate of P (\(R_P\)).
3. Compute the individual work rate of Q (\(R_Q\)) using the formula \(R_Q = R_{P+Q} - R_P\).
4. Calculate the total work completed by P and Q over 8 days.
5. Determine the amount of work remaining.
6. Calculate the duration required for Q to finish the remaining work.

Step 3: Detailed Calculation:
The combined rate of work for P and Q is \(R_{P+Q} = \frac{1}{24}\) of the job per day.
The individual rate of work for P is \(R_P = \frac{1}{32}\) of the job per day.
The individual rate of work for Q is calculated as \(R_Q = R_{P+Q} - R_P = \frac{1}{24} - \frac{1}{32}\).
To perform the subtraction, a common denominator is required. The least common multiple of 24 and 32 is 96.
Thus, \(R_Q = \frac{4}{96} - \frac{3}{96} = \frac{1}{96}\). This indicates that Q, working alone, can complete the entire job in 96 days.

In the 8 days that P and Q worked together, the work completed was \(R_{P+Q} \times 8 = \frac{1}{24} \times 8 = \frac{8}{24} = \frac{1}{3}\) of the job.
The remaining portion of the job is \(1 - \text{Work Done} = 1 - \frac{1}{3} = \frac{2}{3}\) of the job.

Following P's departure, Q must complete the remaining \( \frac{2}{3} \) of the job.
The time Q will take is computed using the formula: \( \frac{\text{Remaining Work}}{R_Q} \).
Time = \( \frac{2/3}{1/96} = \frac{2}{3} \times 96 \)
Time = \( 2 \times \frac{96}{3} = 2 \times 32 = 64 \) days.

Step 4: Conclusion:
Q will require 64 days to complete the remaining work.
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