SOLUTION: The current in ther lazy river moves at a rate of 4mph. Monica'sdinghy motors 6mi upstream in the same time it take to motor 12mi downstream. What is the speed of the dinghy?

Algebra ->  Coordinate Systems and Linear Equations  -> Lessons -> SOLUTION: The current in ther lazy river moves at a rate of 4mph. Monica'sdinghy motors 6mi upstream in the same time it take to motor 12mi downstream. What is the speed of the dinghy?      Log On


   

Question 61093This question is from textbook Intermediate Algebra
: The current in ther lazy river moves at a rate of 4mph. Monica'sdinghy motors 6mi upstream in the same time it take to motor 12mi downstream. What is the speed of the dinghy? This question is from textbook Intermediate Algebra

Found 2 solutions by funmath, venugopalramana:
Answer by funmath(2933) About Me  (Show Source):
You can put this solution on YOUR website!
The current in ther lazy river moves at a rate of 4mph. Monica'sdinghy motors 6mi upstream in the same time it take to motor 12mi downstream. What is the speed of the dinghy?
The distance formula is d=rt. d=distance, r=rate, and t=time. Solve the formula for t.
d%2Fr=rt%2Fr--->d%2Fr=t
distance up stream=6
rate upstream is the rate of the boat (r)- rate of the current(4):r-4
distance downstream=12
rate downstream is the rate of the boat (r)+ rate of the current(4): r+4
The time is the same for both, so set the distance formula solved for time equal to each other.
6%2F%28r-4%29=12%2F%28r%2B4%29
6%28r-4%29%2F%28r-4%29=12%28r-4%29%2F%28r%2B4%29
6=12%28r-4%29%2F%28r%2B4%29
6%28r%2B4%29=12%28r-4%29%28r%2B4%29%2F%28r%2B4%29
6%28r%2B4%29=12%28r-4%29
6r%2B24=12r-48
6r-6r%2B24=12r-6r-48
24=6r-48
24%2B48=6r-48%2B48
72=6r
72%2F6=6r%2F6
12=r
The dingy was moving at 12 mph.
:
Happy Calculating!!!

Answer by venugopalramana(3286) About Me  (Show Source):
You can put this solution on YOUR website!
The current in ther lazy river moves at a rate of 4mph. Monica'sdinghy motors 6mi upstream in the same time it take to motor 12mi downstream. What is the speed of the dinghy?
SPEED OF WATER = 4 MPH
LET SPEED OF DINGHY = S MPH
ITS SPEED UP STREAM = S-4 MPH
DISTANCE TRAVELED UPSTREAM = 6 M
TIME TAKEN = 6/(S-4) HRS..................1
ITS SPEED DOWN STREAM = S+4 MPH
DISATANCE TRAVELLED DOWN STREAM = 12 M
THEN TIME TO TRAVEL UPSTREAM = 12/(S+4) HRS...............2
TIMES ARE EQUAL
6/(S-4) = 12/(S+4)
12(S-4)=6(S+4)
12S-48=6S+24
6S=72
S=12 MPH