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Ramesh and Ganesh can together complete a work in 1616 days. After seven days of working together, Ramesh got sick and his efficiency fell by 30%30 \%. As a result, they completed the work in 1717 days instead of 1616 days. If Ganesh had worked alone after Ramesh got sick, in how many days would he have completed the remaining work?

Solution

✅ Correct Option: 1

We define:

R = Ramesh's normal efficiency (units of work per day)

G = Ganesh's efficiency (units of work per day)

If they complete the work together in 16 days, the total work = 16(R+G)16(R + G) units


Phase 1 (First 7 days): Work done = 7(R+G)7(R + G)

Phase 2 (Next 10 days): Work done = 10(0.7R+G)10(0.7R + G)

Note: 0.7R0.7R because Ramesh's efficiency dropped by 30%, so he works at 70% = 0.7 of his original rate

Total work equation:

7(R+G)+10(0.7R+G)=16(R+G)7(R + G) + 10(0.7R + G) = 16(R + G)


Expanding the left side:

7(R+G)+10(0.7R+G)=16(R+G)7(R + G) + 10(0.7R + G) = 16(R + G)

7R+7G+7R+10G=16R+16G7R + 7G + 7R + 10G = 16R + 16G

14R+17G=16R+16G14R + 17G = 16R + 16G

17G−16G=16R−14R17G - 16G = 16R - 14R

G=2RG = 2R

This means Ganesh is twice as efficient as Ramesh.


After 7 days of normal work together:

Work completed = 7(R+G)7(R + G)

Remaining work = 16(R+G)−7(R+G)=9(R+G)16(R + G) - 7(R + G) = 9(R + G)

Since G=2RG = 2R, we can write R=1R = 1 unit/day and G=2G = 2 units/day

Remaining work = 9(1+2)=279(1 + 2) = 27 units


If Ganesh works at 2 units/day:

Time = WorkRate=272=13.5\tfrac{\text{Work}}{\text{Rate}} = \tfrac{27}{2} = 13.5 days


Answer: 13.5 days

Ganesh is the more efficient worker (twice as fast as Ramesh), so it's reasonable that he can handle the remaining work in a reasonable timeframe.

Key takeaway for future problems: In work problems, we always set up equations based on the fact that total work remains constant, regardless of how it's distributed over time or between workers.

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