Question : A alone can do
Option 1: 9 hours
Option 2: 5 hours
Option 3: 8 hours
Option 4: 4 hours
Correct Answer: 9 hours
Solution :
Let the rate at which A and B can complete the work as
Given that A can do
⇒
Given that B can do
⇒
When A and B work together, their combined rate
⇒
Hence, the correct answer is 9 hours.
