Answer:
15 mph
Step-by-step explanation:
Given: Boat took 2 hours to reach Town A going upstream.
Speed of stream= 3 mph
Time taken to reach back home= 1 hours 20 minutes
Lets assume distance covered one side be "d" and speed of boat in still water be "s".
∴ Speed of boat in upstream=
Speed of boat in downstream=
Also converting into fraction of time taken to reach back home.
Remember; 1 hour= 60 minutes
∴ Time taken to reach back home=
Converting time given into fraction=
hence, Time taken to reach back home is
Now forming equation of boat travelling upstream and downstream, considering distance remain constant.
We know,
⇒
Using distributive property of multiplication
⇒
subtracting both side by
⇒
Adding both side by 6
⇒
taking LCD as 3
⇒
Multiplying both side by
⇒
∴s= 15 mph
Hence, 15 mph is the speed of the boat in still water.