SOLUTION: JOan took 20 min to drive her boat upstream to water ski at her favorite spot. Coming back later in the day, at the same boat speed, took her 15 min. If the current in that part of

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Question 84535This question is from textbook
: JOan took 20 min to drive her boat upstream to water ski at her favorite spot. Coming back later in the day, at the same boat speed, took her 15 min. If the current in that part of the river is 5km per hr,what was her boat speed?This question is from textbook

Answer by checkley75(3666) About Me  (Show Source):
You can put this solution on YOUR website!
DISTANCE=RATE*TIME
D UP STREAM=(R-5)20
D DOWN STREAM=(R+5)15.
SEEING AS THE DISTANCE IS THE SAME WE SET THESE TWO EQUATION EQUAL & WE HAVE:
(R-5)20=(R+5)15
20R-100=15R+75
20R-15R=75+100
5R=175
R=175/5
R=35 KM IS THE BOAT SPEED.
PROOF
(35-5)20=(35+5)15
30*20=40*15
600=600