<PRE><B>Question 1191430</B>
&lt;br&gt;
His downstream rate is 5km/h; his upstream speed is 1km/h.&lt;br&gt;
If the distance in kilometers is d, then a traditional algebraic approach would look something like this:&lt;br&gt;
time downstream = d/5
time upstream = d/1 = d&lt;br&gt;
The total time was 30 minutes, which is 1/2 hour:&lt;br&gt;
{{{d/5+d=1/2}}}&lt;br&gt;
Multiply by 10 to clear fractions:&lt;br&gt;
{{{2d+10d=5}}}
{{{12d=5}}}
{{{d=5/12}}}&lt;br&gt;
ANSWER: 5/12 km&lt;br&gt;
I personally prefer a different solution method:&lt;br&gt;
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.&lt;br&gt;
Now use either the downstream or upstream speeds and times to find the distance.&lt;br&gt;
Downstream:&lt;br&gt;
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.&lt;br&gt;
or...&lt;br&gt;
Upstream:&lt;br&gt;
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.&lt;br&gt;
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