Question 1194880
Same thing, just all as variables.

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A vehicle can maintain a constant speed of R miles per hour relative to the
 water. The vehicle makes a trip upstream to a certain point in U ​minutes; the return trip takes B minutes. What is the speed of the​ current, c ?
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d, the distance of the "certain trip"
U=48 min
B=44 min
R=46 mph
c, unknown speed of current



{{{system(R-c=d/(U/60),R+c=d/(B/60))}}}


{{{(U/60)(R-c)=d,(B/60)(R+c)=d}}}


{{{U(R-c)=d,B(R+c)=d}}}


{{{UR-Uc=BR+Bc}}}


{{{UR-BR=Bc+Uc}}}


{{{(UR-BR)/(B+U)=c}}}

{{{OR}}}

{{{highlight(c=R((U-B)/(U+B)))}}}------and you just plug in the given values and find c.


Many people would choose to use the given values at the beginning, instead of solving the example all in variables.


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Usually one would do like so:
<pre>
              SPEED            TIME          DISTANCE

upstream        (46-c)          (48/60)         d

downstream      (46+c)          (44/60)         d
</pre>
{{{(46-c)(48/60)=(46+c)(44/60)}}}


{{{(46-c)(48)=(46+c)(44)}}}

{{{12(46-c)=11(46+c)}}}

{{{12*46-12c=11*46+11c}}}

{{{12*46-11*46=11c+12c}}}

{{{46=23c}}}

{{{highlight(c=2)}}}