document.write( "Question 761851: Tony'a outboard can drive her boat at 7mph in still water. It takes her 10 minutes more to reach her friends camp 4 miles up the river than to return to her camp down river. What is the speed of the current?\r
\n" ); document.write( "\n" ); document.write( "I have already asked this question on here before but got an incorrect answer. Be aware that it takes Tonya 10 minutes MORE not just 10 minutes. Here is my attempt
\n" ); document.write( "going: 4=(7-c)*(t+10) returning: 4=(7+c)*t
\n" ); document.write( "$=(7-c)*((4/7+c)+10)
\n" ); document.write( "Where do I go from here? You are so wonderful thank you so much!
\n" ); document.write( "Forever in debt to strangers, Abby \n" ); document.write( "

Algebra.Com's Answer #463520 by josmiceli(19441) $\"\"$ $\"About$

You can put this solution on YOUR website!
Let $\"+c+\"$ = the speed of the current
\n" ); document.write( " $\"+7+-+c+\"$ = her speed going against the current
\n" ); document.write( " $\"+7+%2B+c+\"$ = her speed going with the current
\n" ); document.write( "Let $\"+t+\"$ = her time going with the current
\n" ); document.write( " $\"+t+%2B+10+\"$ = her time going against the current
\n" ); document.write( "-------------------------
\n" ); document.write( "Against the current:
\n" ); document.write( "(1) $\"+4+=+%28+7+-+c+%29%2A%28+t+%2B+10+%29+\"$
\n" ); document.write( "With the current:
\n" ); document.write( "(2) $\"+4+=+%28+7+%2B+c+%29%2At+\"$
\n" ); document.write( "-------------------
\n" ); document.write( "(1) $\"+4+=+7t+-+c%2At+%2B+70+-+10c+\"$
\n" ); document.write( "(1) $\"+7t+-+c%2At+=+10c+-+66+\"$
\n" ); document.write( "(1) $\"+t%2A%28+7+-+c+%29+=+10c+-+66+\"$
\n" ); document.write( "(1) $\"+t+=+%28+10c+-+66+%29+%2F+%28+7-c+%29+\"$
\n" ); document.write( "and
\n" ); document.write( "(2) $\"+4+=+%28+7+%2B+c+%29%2At+\"$
\n" ); document.write( "(2) $\"+t+=+4%2F%28+7+%2B+c+%29+\"$
\n" ); document.write( "By substitution:
\n" ); document.write( "(1) $\"+4%2F%28+7+%2B+c+%29+=+%28+10c+-+66+%29+%2F+%28+7-c+%29+\"$
\n" ); document.write( "Multiply both sides by $\"+%28+7%2Bc+%29%2A%28+7-c+%29+\"$
\n" ); document.write( "(1) $\"+4%2A%28+7-c+%29+=+%28+10c+-+66+%29%2A%28+7%2Bc+%29+\"$
\n" ); document.write( "(1) $\"+4%2A%28+7-c+%29+=+2%2A%28+5c+-+33+%29%2A%28+7%2Bc+%29+\"$
\n" ); document.write( "(1) $\"+14+-+2c+=+35c+-+231+%2B+5c%5E2+-+33c+\"$
\n" ); document.write( "(1) $\"+5c%5E2+%2B+4c+-+245+=+0+\"$
\n" ); document.write( "Use quadratic formula
\n" ); document.write( " $\"+c+=+%28-b+%2B-+sqrt%28+b%5E2+-+4%2Aa%2Ac+%29%29+%2F+%282%2Aa%29+\"$
\n" ); document.write( " $\"+a+=+5+\"$
\n" ); document.write( " $\"+b+=+4+\"$
\n" ); document.write( " $\"+c+=+-245+\"$ ( not the same c as current )
\n" ); document.write( " $\"+c+=+%28-4+%2B-+sqrt%28+4%5E2+-+4%2A5%2A%28-245%29+%29%29+%2F+%282%2A5%29+\"$
\n" ); document.write( " $\"+c+=+%28-4+%2B-+sqrt%28+16+%2B+4900%29%29+%2F+10+\"$
\n" ); document.write( " $\"+c+=+%28-4+%2B-+sqrt%28+4916%29%29+%2F+10+\"$
\n" ); document.write( " $\"+c+=+%28-4+%2B+70.114+%29%2F+10+\"$
\n" ); document.write( " $\"+c+=+66.114+%2F+10+\"$
\n" ); document.write( " $\"+c+=+6.611+\"$
\n" ); document.write( "The speed of the current is 6.611 mi/hr
\n" ); document.write( "check:
\n" ); document.write( "(2) $\"+4+=+%28+7+%2B+c+%29%2At+\"$
\n" ); document.write( "(2) $\"+4+=+%28+7+%2B+6.611+%29%2At+\"$
\n" ); document.write( "(2) $\"+4+=+13.611t+\"$
\n" ); document.write( "(2) $\"+t+=+.294+\"$
\n" ); document.write( "and
\n" ); document.write( "(1) $\"+4+=+%28+7+-+6.611+%29%2A%28+t+%2B+10+%29+\"$
\n" ); document.write( "(1) $\"+4+=+.389t+%2B+3.89+\"$
\n" ); document.write( "(1) $\"+.389t+=+.11+\"$
\n" ); document.write( "(1) $\"+t+=+.283+\"$
\n" ); document.write( "This method should be OK, but it doesn,t
\n" ); document.write( "exactly check- maybe you can find error
\n" ); document.write( "Hope this helps\r
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( " \n" ); document.write( "

\n" );