SOLUTION: The speed of about in still water is 15km/hr.it can go 45 km upstream and return downstream to the original point in 6 hours 45 minutes. Find the speed of the stream.

Algebra ->  Rate-of-work-word-problems -> SOLUTION: The speed of about in still water is 15km/hr.it can go 45 km upstream and return downstream to the original point in 6 hours 45 minutes. Find the speed of the stream.      Log On


   

Question 954052: The speed of about in still water is 15km/hr.it can go 45 km upstream and return downstream to the original point in 6 hours 45 minutes. Find the speed of the stream.
Found 2 solutions by josgarithmetic, hemu_da:
Answer by josgarithmetic(39631) About Me  (Show Source):
You can put this solution on YOUR website!
r=15
c=unknown, the current
r+c=upstream speed
r-c=downstream speed
T=total time of 6%263%2F4 hours
d=45

__________________speed_________time__________distance
upstream__________r-c____________d/(r-c)_____________d
downstrm__________r+c____________d/(r+c)_____________d
Total_____________________________T

Uniform Rates Rule for Travel, RT=D

The basic equation setup all in symbolic form: highlight%28d%2F%28r-c%29%2Bd%2F%28r%2Bc%29=T%29
Solve for c.

Answer by hemu_da(13) About Me  (Show Source):
You can put this solution on YOUR website!
Let the speed of streem is - a km/hr.

Given - speed of a boat in still water is 15 km/hr.
Now, speed against the streem is - (15-a) km/hr.
And with the streem is - (15+a) km/hr.
Boat goes 45 km against the streem and come back in 6 hr 45 min.
Time to take to cover 45 km against the streem is--

45%2F%2815-a%29 hr.
.
.
And time with the streemis-
45%2F%2815%2Ba%29 hr.

Hence both are equal to 6 hr 45 min or 6+%283%2F4%29 hr or 27%2F4 hr.
..
..
i.e.
%2845%2F%2815-a%29%29+%2B+%2845%2F%2815%2Ba%29%29+=+%2827%2F4%29
.
.
after simplifying this eq we can get--
.
. a = 5 km/hr.. Ans.