B can work 3 times faster than A. They work together on a task and complete it in a day. How long does it take for B alone to complete the task ?

Part of task completed by A in a day = 1/x Part of task completed by B in a day = 3/x (B is thrice as efficient as A) (1/x)+(3/x) = 1 4/x = 1 x = 4 B completes 3/4th of the task in a day. He takes 4/3 days to complete the entire task. 4/3 days = (4/3*24) hours = 32 hours