Asked by Urgent

Briana can row 4 miles per hour is still water. It takes as long to row 8 miles upstream as 24 miles downstream. How fast is the current?
Answered by Damon
speed of current = u
speed upstream = (u-4)
speed downstream = (u+4)

8 = (u-4) T so T = 8/(u-4)
24 = (u+4) T so T = 24/(u+4)

8/(u-4) = 24/(u+4)

24(u-4) = 8 (u+4)

24 u - 96 = 8 u + 32

16 u = 128

u = 8
Answered by Urgent
How did you do 8/(u-4) which turned in to 8(u-4)
Answered by Al
Cross multiplication
8 24
______ = ______

u-4 u+4

8(u+4) = 24(u-4)
8u + 32 = 24u - 96
8u = 24u - 128
-16u = -128
u = 8
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