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Floating Down a River - How Would You Solve It?

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by palvarez » Mon Nov 16, 2009 10:18 am
(v-3)t = (v+3)(t-0.5) = 90

(v+3)/(v-3) = t/(t-.5)

2v/6 = 2(2t-.5) = 4t - 1
v = 12t-3


(12t-6)t = 90
(2t-1)t = 15 = 5.3

t = 3 (upsteam)
downstream = 2.5
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by cbenk121 » Mon Nov 16, 2009 12:45 pm
palvarez wrote:(v-3)t = (v+3)(t-0.5) = 90

(v+3)/(v-3) = t/(t-.5)

2v/6 = 2(2t-.5) = 4t - 1
v = 12t-3


(12t-6)t = 90
(2t-1)t = 15 = 5.3

t = 3 (upsteam)
downstream = 2.5
How'd you move from "(v+3)/(v-3) = t/(t-.5)" to "2v/6 = 2(2t-.5)"?
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by palvarez » Mon Nov 16, 2009 12:49 pm
a/b = c/d

(a+b)/(a-b) = (c+d)/(c-d)

a/b = c/d
add 1 both sides
(a+b)/b = (c+d)/d
subtract 1 both sides
(a-b)/b = (c-d)/d

Divide both

(a+b)/(a-b) = (c+d)/(c-d)
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