Question : To do a certain work, the ratio of the efficiencies of A and B is 7 : 5. Working together, they can complete the same work in
Option 1: 18 days
Option 2: 15 days
Option 3: 16 days
Option 4: 21 days
Correct Answer: 18 days
Solution :
Let the efficiency of A be
Given that the ratio of the efficiencies of A and B is 7 : 5, for some constant
The total amount of work done by A and B together in one day.
Given that A and B together can complete the work in
The total work
The time it will take for A to complete 60% of the work alone.
The amount of work A needs to do =
The time it takes for A to complete this amount of work
Hence, the correct answer is 18 days.
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