Question

A man rows a boat at a speed of 15 mph in still water. Find the speed of the river if it takes her 4 hours 30 minutes to row a boat to a place 30 miles away and return. 1) 5 mph 2) 10 mph 3) 12 mph 4) 20 mph

Answer 1

Answer:

option1 -  5 mph

Please mark the answer as "The Brainliest answer" if it helps

Step-by-step explanation:

one side Distance = 30 miles

Let say speed of river = x miles/hr

Speed with Stream = 15 + x  miles /hr

Speed against stream =  15 - x miles/hr

Total time taken = 4hr 30 minuts = 4.5 hr = 9/2 hr

Total Time  =  30/(15+x)   +  30/(15-x)  = 9/2

30(15-x + 15 + x) = (9/2)  * ( 15+x)(15-x)

2 * 30 * 30 = 9 * (15^2  - x^2)

200 = 225 - x^2

x^2 = 25

x = 5 miles/hr

option 1  is right answer