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A man started a job. Starting from the second day, each day a new man joined with which the capacity of each man doubled. The job was completed in 6 days. On which day will the job be completed if the joining of a new man on a day results in each man working at thrice the rate as he did on the previous day?
1. 6th
2. 5th
3. 4th
4. 3rd

Shivraj , 9 Years ago
Grade 12th pass
anser 1 Answers
Sourabh Singh

To solve this problem, we need to analyze how the work capacity changes each day as new men join and how this affects the completion of the job. Let's break it down step by step.

Understanding the Work Rate

Initially, we have one man working on the job. Let's assume this man's work capacity is represented as 1 unit of work per day. Now, on the second day, a new man joins, and according to the problem, the capacity of each man doubles. This means that on the second day, each man (the original and the new one) will work at a rate of 2 units per day.

Daily Work Calculation

Now, let's summarize the work done each day:

  • Day 1: 1 man x 1 unit = 1 unit
  • Day 2: 2 men x 2 units each = 4 units
  • Day 3: 3 men x 4 units each = 12 units
  • Day 4: 4 men x 8 units each = 32 units
  • Day 5: 5 men x 16 units each = 80 units
  • Day 6: 6 men x 32 units each = 192 units

How the Rate Changes with New Men

Now, if a new man joins on the second day and it results in each man working at thrice the rate of the previous day, the calculations change significantly:

  • Day 1: 1 man x 1 unit = 1 unit
  • Day 2: 2 men x 3 units each = 6 units
  • Day 3: 3 men x 9 units each = 27 units
  • Day 4: 4 men x 27 units each = 108 units
  • Day 5: 5 men x 81 units each = 405 units
  • Day 6: 6 men x 243 units each = 1458 units

Accumulating Total Work

With this new rate, we can accumulate the total work done over the days. Assuming the job requires a certain total of work units, we can see the exponential growth in the work capacity:

  • Total work by Day 1: 1 unit
  • Total work by Day 2: 1 + 6 = 7 units
  • Total work by Day 3: 7 + 27 = 34 units
  • Total work by Day 4: 34 + 108 = 142 units
  • Total work by Day 5: 142 + 405 = 547 units
  • Total work by Day 6: 547 + 1458 = 2005 units

Determining Job Completion

Given that the job was completed in 6 days under the initial doubling rule, we now want to find out when the work will be completed under the new condition where each man works at thrice the rate. Based on our calculations, we can conclude that the job will be completed well before the sixth day due to the rapid increase in productivity.

Hence, under the new work condition, the job will actually be completed by the end of Day 4, as the cumulative work will exceed the required amount. Therefore, the answer is:

4th Day

Last Activity: 9 Years ago
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