SOLUTION: Jane took 15 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 10 min. If the current in that part of

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Question 1092089: Jane took 15 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 10 min. If the current in that part of the river is 4 km per hr, what was her boat speed in still water?
Found 3 solutions by jorel1380, josmiceli, MathTherapy:
Answer by jorel1380(3719)   (Show Source): You can put this solution on YOUR website!
Let s be the speed of Jane's boat in still water. Then:
.25(s-4)=.2(s+4) (.25=1/4 hour=15 min; .2=1/5 hr=10 min)
.25s-1=.2s+.8
.05s=1.8
s=36
Jane's boat goes 36 kmh in still water
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Answer by josmiceli(19441)   (Show Source): You can put this solution on YOUR website!
Convert minutes to hrs
hrs
hrs
Let = her speed in still water
-----------------------------------
Going upsteam:
(1) km
Going downstream:
(2) km
-------------------------------

Multiply both sides by



The speed in still water is 20 km/hr
---------------------------------
check:
(1)
(1)
(1) km
and
(2)
(2)
(2) km
OK

Answer by MathTherapy(10556)   (Show Source): You can put this solution on YOUR website!

Jane took 15 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 10 min. If the current in that part of the river is 4 km per hr, what was her boat speed in still water?
Let sped in still water be S

Then we get the following DISTANCE equation: 





6(S - 4) = 4(S + 4) ------- Cross-multiplying 

6S - 24 = 4S + 16

6S - 4S = 16 + 24

2S = 40

S, or speed in still water = 

IGNORE anyone who says otherwise! 

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