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Question

A, B and C can complete a work in x, 1.5x and 2x days respectively. If they complete the work together, in what ratio should they be paid ?  

This question was previously asked in
CDS I 2023 English Previous Year Paper (16-April-2023)
The correct answer is

6 : 4 : 3

Understanding Work, Time, and Wages Ratio

This question involves the concept of work, time, and how wages should be distributed when multiple people work together to complete a task. The fundamental principle here is that the payment received for completing a work should be proportional to the amount of work done by each individual.

When individuals work on the same project for the same duration (until the project is completed), the amount of work done by each person is directly proportional to their efficiency or their daily work rate.

Let's analyze the information given about A, B, and C:

  • A completes the work in \(x\) days.
  • B completes the work in \(1.5x\) days.
  • C completes the work in \(2x\) days.

The time taken to complete the work is inversely proportional to the work rate. A person who takes less time has a higher work rate, and vice-versa.

Calculating Individual Daily Work Rates

The daily work rate is the fraction of the work completed in one day.

  • A's daily work rate = \(\frac{1}{\text{Time taken by A}} = \frac{1}{x}\)
  • B's daily work rate = \(\frac{1}{\text{Time taken by B}} = \frac{1}{1.5x} = \frac{1}{\frac{3}{2}x} = \frac{2}{3x}\)
  • C's daily work rate = \(\frac{1}{\text{Time taken by C}} = \frac{1}{\text{Time taken by C}} = \frac{1}{2x}\)

Determining the Payment Ratio

When A, B, and C work together and complete the task, they work for the same total duration. Therefore, their payment should be in the ratio of their daily work rates.

Ratio of payments for A : B : C = (A's rate) : (B's rate) : (C's rate)

Ratio = \(\frac{1}{x} : \frac{2}{3x} : \frac{1}{2x}\)

To simplify this ratio, we need to multiply each term by the least common multiple (LCM) of the denominators (\(x\), \(3x\), \(2x\)). The LCM of \(x\), \(3x\), and \(2x\) is \(6x\).

Multiply each term by \(6x\):

Ratio = \(\left(\frac{1}{x} \times 6x\right) : \left(\frac{2}{3x} \times 6x\right) : \left(\frac{1}{2x} \times 6x\right)\)

Ratio = \(6 : \left(\frac{2 \times 6x}{3x}\right) : \left(\frac{1 \times 6x}{2x}\right)\)

Ratio = \(6 : \left(\frac{12x}{3x}\right) : \left(\frac{6x}{2x}\right)\)

Ratio = \(6 : 4 : 3\)

Thus, A, B, and C should be paid in the ratio of \(6 : 4 : 3\) when they complete the work together.

Summary of Work Rates and Payment Ratio

Person Time Taken Daily Work Rate
A \(x\) days \(\frac{1}{x}\)
B \(1.5x\) days (\(= \frac{3}{2}x\) days) \(\frac{1}{1.5x} = \frac{2}{3x}\)
C \(2x\) days \(\frac{1}{2x}\)

Ratio of Daily Work Rates = \(\frac{1}{x} : \frac{2}{3x} : \frac{1}{2x} = 6:4:3\)

The ratio of payment should be \(6:4:3\).

Revision Table: Work and Wages Concepts

Concept Explanation Relationship
Work Rate Amount of work done per unit of time (e.g., per day). Work Rate = \(\frac{1}{\text{Time Taken}}\)
Total Work Usually considered as 1 unit or a specific amount like LCM of times. Total Work = Rate \(\times\) Time
Payment Ratio How total wages are divided among workers. Proportional to Work Done by each worker. If working together for the same time, proportional to their Work Rates.
Efficiency Synonym for work rate; indicates how effectively work is done. Higher efficiency means higher work rate and less time taken.

Additional Information: Calculating Combined Work Time

Although not directly asked, we can also calculate the time taken if A, B, and C work together. Their combined daily work rate is the sum of their individual rates:

Combined rate = (A's rate) + (B's rate) + (C's rate)

Combined rate = \(\frac{1}{x} + \frac{2}{3x} + \frac{1}{2x}\)

To add these fractions, find a common denominator, which is \(6x\).

Combined rate = \(\frac{1 \times 6}{6x} + \frac{2 \times 2}{6x} + \frac{1 \times 3}{6x}\)

Combined rate = \(\frac{6}{6x} + \frac{4}{6x} + \frac{3}{6x}\)

Combined rate = \(\frac{6 + 4 + 3}{6x} = \frac{13}{6x}\)

The time taken to complete the work together is the reciprocal of the combined rate:

Time together = \(\frac{1}{\text{Combined rate}} = \frac{1}{\frac{13}{6x}} = \frac{6x}{13}\) days.

This shows that they complete the work in \(\frac{6x}{13}\) days working together, and their payment ratio is based on their efficiencies during this time.

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Similar Questions

  1. If x men working x hours per day can do x units of work in x days, then y men working y hours per day in y days would be able to do k units of work. What is the value of k?

  2. X and Y can do a piece of work in 45 days and 40 days respectively. They begin to work together, but X leaves after n days and then Y completes the remaining work in 23 days. What is n equal to ?

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Important Questions from Time and Work

  1. Mohan can do a piece of work in 10 days and Sohan in 15 days. They started working together, but after 3 days Mohan left the work . What time will Sohan take to finish the work?

  2. A tank is filled in 8 hours by three taps A, B and C. The tap C is thrice as fast as B and B is twice as fast as A. How much time will pipe B alone take to fill the tank?

  3. Had been one menless, then the number of days required to do a piece of work would have been one more. If the number of Man. Days required to complete the work is 56, how many workers were there?

  4. A can do a piece of work in 16 hours, B and C can do it in 8 hours while A and C can do it 12 hours. How long will B alone take to do it?

  5. lf 12 men can do a work in 20 days, in how many days will the work be done by 15 men-
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