Answer:
Time spent rowing down stream 
Speed of boat in still water 
Step-by-step explanation:
Let speed of boat in still water be 
Speed of current 
Speed of boat down stream = 
Distance rowed down stream = 2400 m
Time spent rowing down stream =
= 
Speed of boat up stream = 
Distance rowed up stream = 
Time spent rowing up stream = 
We know that,
So,

Cross multiplying

Dividing both sides by 



Adding 60 to both sides.


Subtracting both sides by 


Dividing both sides by 5.

∴ 
Speed of boat in still water 
Time spent rowing down stream =