SOLUTION: A river is flowing downstream at rate of 2km/h.
Murray can swim at a rate of 3km/h.
Murray jumps in and swims downstream for a certain distance then turns around and swims upst
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-> SOLUTION: A river is flowing downstream at rate of 2km/h.
Murray can swim at a rate of 3km/h.
Murray jumps in and swims downstream for a certain distance then turns around and swims upst
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Question 1191430: A river is flowing downstream at rate of 2km/h.
Murray can swim at a rate of 3km/h.
Murray jumps in and swims downstream for a certain distance then turns around and swims upstream back to the start. In total it takes 30 minutes.
How far did Murray swim downstream?
I got 15/16 km but the answer is 5/12 km. How did it get to 5/12km? Found 2 solutions by greenestamps, Alan3354:Answer by greenestamps(13200) (Show Source):
His downstream rate is 5km/h; his upstream speed is 1km/h.
If the distance in kilometers is d, then a traditional algebraic approach would look something like this:
time downstream = d/5
time upstream = d/1 = d
The total time was 30 minutes, which is 1/2 hour:
Multiply by 10 to clear fractions:
ANSWER: 5/12 km
I personally prefer a different solution method:
His downstream rate of 5km/h is 5 times his upstream speed; since the distances downstream and back are the same, he spends 5 times much time coming upstream as going downstream. That means he spends 1/6 of the total time going downstream and 5/6 of his total time coming back upstream.
Now use either the downstream or upstream speeds and times to find the distance.
Downstream:
1/6 of 30 minutes, or 1/6 of 1/2 hour, is 1/12 hour; 1/12 hour at 5km/h is (5)(1/12) = 5/12 km.
or...
Upstream:
5/6 of 1/2 hour is 5/12 hour; 5/12 of an hour at 1km/h is (1)(5/12) = 5/12 km.
You can put this solution on YOUR website! A river is flowing downstream at rate of 2km/h. Note: they always flow downstream.
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Murray can swim at a rate of 3km/h.
Murray jumps in and swims downstream for a certain distance then turns around and swims upstream back to the start. In total it takes 30 minutes.
How far did Murray swim downstream?
t1 = d/(3+2) is the time swimming downstream.
t2 = d/(3-2) is the time swimming upstream.
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t1 + t2 = 0.5 hours (given)
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d/5 + d = 0.5
d + 5d = 2.5
6d = 2.5
d = 2.5/6 = 5/12 km
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I got 15/16 km but the answer is 5/12 km. How did it get to 5/12km?
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Might be interesting to see how you got 15/16.
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The average speed of a round-trip is 2*v1*v2/(v1+v2)
avg speed = 2*5*1/(5+1) = 10/6 = 5/3 km/hr
d = r*t
d = (5/3)*0.5 = 5/6 km round trip
----> 5/12 km each way
