SOLUTION: Rita rows 12 km upstream and 12 km downstream in 3 hours. The speed of her boat in still water is 9 km/hr. Find the speed of the stream.
I am thinking that I need to use the f
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Question 58639This question is from textbook
: Rita rows 12 km upstream and 12 km downstream in 3 hours. The speed of her boat in still water is 9 km/hr. Find the speed of the stream.
I am thinking that I need to use the formula Time = distance/rate?
This question is from textbook
Found 2 solutions by checkley71, stanbon:
Answer by checkley71(8403) (Show Source): You can put this solution on YOUR website!
d=rt or
d/r=t
12/(9+x)+12/(9-x)=3
[12(9-x)+12(9+x)]/(9+x)(9-x)=3
(108-12x+108+12x)/(81-x^2)=3
216/(81-x^2)=3
(81-x^2)3=216
243-3x^2=216
-3x2=216-243
-3x^2=-27
x^2=-27/-3
x^2=9
x=sqrt9
x=3 km/hr for the current
proof
12/(9+3)+12/(9-3)=3
12/12+12/6=3
1+2=3
3=3
Answer by stanbon(75887) (Show Source): You can put this solution on YOUR website!
Rita rows 12 km upstream and 12 km downstream in 3 hours. The speed of her boat in still water is 9 km/hr. Find the speed of the stream.
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Let the speed of the current be "c".
Upstream DATA:
distance= 12 km ; rate= 9-c ; time=d/r=12/(9-c)
---------------
Downstream DATA:
distance = 12 km; rate = 9+c time=d/r = 12/(9+c)
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EQUATION:
time+time=3 hours
12/(9-c)+12/(9+c)= 3
12(9+c) +12(9-c) = 3(81-c^2)
108+108=243-3c^2
3c^2=27
c^2=9
c=3 km/hr (speed of the current)
cheers,
Stan H.
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