Answer:
The speed of boat in still water is 11 miles per hour
The speed of current is 10 miles per hour .
Step-by-step explanation:
Given as :
The distance cover by boat in downstream =
= 147 miles
The time taken by boat in downstream trip =
= 7 hours
The distance cover by boat in upstream =
= 147 miles
The time taken by boat in upstream trip =
= 147 hours
Let The speed of boat in still water =
= x mph
And The speed of the current =
= y mph
Now, According to question
Speed = 
For downstream
+
= 
or, x + y = 
I.e x + y = 21 mph ..........1
For upstream
+
= 
or, x - y = 
I.e x - y = 1 mph ..........2
Now, Solving Eq 1 and 2
I.e (x + y) + (x - y) = 21 + 1
Or, (x + x) + (y - y) = 22
Or, 2 x = 22
∴ x = 
I.e x = 11 mph
So, speed of boat = x = 11 miles per hour
Again, put The value of x in Eq 2
So, x - y = 1 mph
I.e 11 - y = 1
∴, y = 11 - 1
I.e y = 10 mph
So, speed of current = y = 10 miles per hour
Hence The speed of boat in still water is 11 miles per hour , and The speed of current is 10 miles per hour . Answer