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Question

Mahesh and Suresh can complete a work alone in 20 days and 30 days respectively. They received Rs. 3300 for completing the work together. What is the share of Mahesh?

The correct answer is

Rs. 1980

Understanding Work and Wages Problems

This problem involves the concept of work and wages. When multiple individuals work together to complete a task and receive a total wage, the wage is typically distributed among them in proportion to the amount of work they complete. If they work for the same duration (as implied when they complete the same total work together), their share of the wages is proportional to their efficiency or their rate of doing work.

Calculating Individual Work Rates

The rate at which a person completes work is the inverse of the time taken to complete the entire work alone. If Mahesh takes 20 days to complete the work alone, his daily work rate is $\frac{1}{20}$ of the total work.

  • Mahesh's time to complete work alone = 20 days
  • Mahesh's daily work rate = $\frac{1}{20}$ work per day

Similarly, if Suresh takes 30 days to complete the work alone, his daily work rate is $\frac{1}{30}$ of the total work.

  • Suresh's time to complete work alone = 30 days
  • Suresh's daily work rate = $\frac{1}{30}$ work per day

Determining the Ratio of Shares

Since Mahesh and Suresh work together to complete the work, and assuming they work for the same duration until the work is finished, their shares in the total wage will be directly proportional to their individual work rates (efficiency).

The ratio of their daily work rates is:

Mahesh's Rate : Suresh's Rate = $\frac{1}{20} : \frac{1}{30}$

To simplify this ratio and work with whole numbers, we can multiply both parts of the ratio by the least common multiple (LCM) of 20 and 30, which is 60.

Ratio = $\frac{1}{20} \times 60 : \frac{1}{30} \times 60$

Ratio = $3 : 2$

So, the total wage of Rs. 3300 should be divided between Mahesh and Suresh in the ratio $3:2$.

Calculating Mahesh's Share

The total ratio parts are $3 + 2 = 5$.

Mahesh's share corresponds to 3 out of these 5 parts.

Total wage received for completing the work = Rs. 3300

Mahesh's share = (Mahesh's ratio part / Total ratio parts) $\times$ Total Wage

Mahesh's share = $\frac{3}{5} \times 3300$

Mahesh's share = $3 \times \frac{3300}{5}$

Mahesh's share = $3 \times 660$

Mahesh's share = Rs. 1980

We can also calculate Suresh's share for completeness:

Suresh's share = (Suresh's ratio part / Total ratio parts) $\times$ Total Wage

Suresh's share = $\frac{2}{5} \times 3300$

Suresh's share = $2 \times 660$

Suresh's share = Rs. 1320

Check: Mahesh's share + Suresh's share = $1980 + 1320 = 3300$. This matches the total wage.

Summary of Shares

Person Time Alone (days) Daily Rate Ratio Part Share (Rs.)
Mahesh 20 $\frac{1}{20}$ 3 1980
Suresh 30 $\frac{1}{30}$ 2 1320
Total - - 5 3300

Thus, the share of Mahesh for completing the work together is Rs. 1980.

Revision Table: Work and Wages Concepts

Concept Explanation Application in Problem
Work Rate Amount of work done per unit of time. It's the reciprocal of the time taken to complete the whole work. Mahesh's rate = $1/20$, Suresh's rate = $1/30$.
Ratio of Shares When people work together for the same time, wages are divided in the ratio of their work rates (efficiency). Ratio of shares = Mahesh's Rate : Suresh's Rate = $3:2$.
Total Ratio Parts Sum of the parts in the ratio used for distribution. Total parts = $3+2=5$.
Individual Share Calculation (Individual's Ratio Part / Total Ratio Parts) $\times$ Total Wage. Mahesh's share = $(3/5) \times 3300$.

Additional Information: Alternative Approach using LCM (Total Work)

An alternative method to solve work and wages problems is using the LCM of the times taken to represent the 'total work units'.

  • Time for Mahesh = 20 days
  • Time for Suresh = 30 days

Let the total work be the LCM of 20 and 30, which is 60 units.

  • Mahesh's daily efficiency = Total work / Mahesh's time = $60 / 20 = 3$ units/day
  • Suresh's daily efficiency = Total work / Suresh's time = $60 / 30 = 2$ units/day

When they work together for the same period, their shares are proportional to their daily efficiency.

Ratio of efficiencies = Mahesh's efficiency : Suresh's efficiency = $3 : 2$.

This ratio is the same as the ratio of rates calculated earlier. The total wage (Rs. 3300) is divided in this $3:2$ ratio.

Mahesh's share = $\frac{3}{3+2} \times 3300 = \frac{3}{5} \times 3300 = 3 \times 660 = \text{Rs. } 1980$.

This LCM method often makes the calculation of the ratio simpler by avoiding fractions initially.

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Important Questions from Work Efficiency

  1. A and B working together can complete a job in 30 days. The ratio of their efficiencies is 3 : 2. In how many days can the faster person complete the job?

  2. A takes 15 days to complete \(\frac{5}{7} \)  of a work. With the help of B, they finish the whole work in 12 days. In how many days, B alone will complete the same work

  3. A alone can complete a work in 14 days and B alone can complete the same work in 21 days. A and B start the work together but A leaves the work after 4 days of the starting of work. In how many days B will complete the remaining work?

  4. For completing a certain work, A is 50% less efficient than B and B is 50% more efficient than C. Working together A, B and C can complete the work in 48 days. A alone can complete the same work in:

  5. 30 persons can do a piece of work in 24 days. How many more persons are required to complete the work in 20 days?

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