<PRE><B>Question 521817</B>
d = r*t is the basic distance equation:  distance = rate * time
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d = 16 miles
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r = j - c when going upstream
j -c = jetski speed minus current speed
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r = j+c when going downstream
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t = 1/2 hr going upstream
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16 = 1/2*(j-c)
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t = 1/3 hr going downstream
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16 = 1/3(j+c)
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16=16
so
1/2*(j-c) = 1/3*(j+c)
(j-c)/2 = (j+c)/3
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Cross multiply
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3(j-c) = 2(j+c)
3j -3c = 2j + 2c
j = 5c
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substitute
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16 = 1/2*(5c-c)
32 = 4c
4c = 32
c = 8
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Substitute
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j = 5c
j = 40
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Check distances traveled in the given times to determine if this answer is correct.
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1/2*(40-8) = 16
1/3*(40+8) = 16
Correct.
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Answer:  The speed of the jetski in still water is 40 mph, and the speed of the current is 8 mph.</PRE>