A completes 60% of a task in 15 days and then takes the help of B and C. B is 50% as efficient as A is and C is 50% as efficient as B is. In how many more days will they complete the work?
Answer: A
A completes 60% of the task in 15 days i.e., he completes 4% of the task in a day.
B is 50% as efficient as A is, therefore, B will complete 2% of the task in a day.
C is 50% as efficient as B is, therefore, C will complete 1% of the task in a day.
Together, A, B and C will complete 4 + 2 + 1 = 7% of the work in a day.
They have another 40% of the task to be completed. Therefore, they will take 40 / 7 more days to complete the task.