Isha can do a certain piece of work in 20 days. Isha and Smriti can together do the same work in 16 days, and Isha, Smriti and Ashlesha can do the same work together in 8 days. In how many days can Isha and Ashlesha do the same work? 

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  1. \(\frac{79}{10}\)
  2. \(\frac{80}{9}\)
  3. \(\frac{76}{11}\)
  4. \(\frac{89}{9}\)

Answer (Detailed Solution Below)

Option 2 : \(\frac{80}{9}\)
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Detailed Solution

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Given:

Isha can complete the work in 20 days.

Isha and Smriti together can complete the work in 16 days.

Isha, Smriti, and Ashlesha together can complete the work in 8 days.

Formula used:

Work rate = 1 / Time taken

Calculation:

Let the work rates of Isha, Smriti, and Ashlesha be LCM(20, 16, 8) = 80 units

Efficiency of Isha = 80/20 = 4 unit per day

Efficiency of Isha + Efficiency of Smriti = 80/16 = 5 unit per day

Efficiency of Isha + Efficiency of Smriti + Efficiency of Ashlesha = 80/8 = 10 units per day

Efficiency of Smriti = 5 - 4 = 1 unit per day

Efficiency of Ashlesha = 10 - 5 = 5 units per day

Combined efficiency of Isha and Ashlesha = 4 + 5 = 9 units per day

Time taken by Isha and Ashlesha to complete the work together = 80/9 days.

Option 2 is the correct answer.

 

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