document.write( "Question 1041826: A child is running on a moving sidewalk in an airport. When he runs against the sidewalk's motion, he travels 75 feet in 15 seconds. When he runs with the sidewalk's motion, he travels 99 feet in 9 seconds. What is the rate of the child on a still sidewalk and what is the rate of the moving sidewalk? \n" ); document.write( "

Algebra.Com's Answer #656739 by ikleyn(52803) $\"\"$ $\"About$

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document.write( " =  5 = u - v,    \r\n" );
document.write( " = 11 = u + v,\r\n" );
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document.write( "where  is the boy's speed relative to the floor when moving against . . .\r\n" );
document.write( " is the boy's speed relative to the floor when moving with . . .\r\n" );
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document.write( "u is the boy's speed relative to the moving sidewalk, v is the speed of sidewalk relative to the floor.\r\n" );
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document.write( "S, you have this two basic equations:\r\n" );
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document.write( "u - v =  5,   (1)   and\r\n" );
document.write( "u + v = 11.   (2)\r\n" );
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document.write( "Add eqns(1) and (2) (both sides). You will get \r\n" );
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document.write( "2u = 5 + 11 = 16  --->  u =  = 8  - speed of the boy rel. to the sidewalk.\r\n" );
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document.write( "The v = u - 5 = 8 - 5 = 3  is the speed of sidewalk rel. to the floor.\r\n" );
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document.write( "Answer.  8  and 3 .\r\n" );
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\n" ); document.write( "\n" ); document.write( "For details see these lessons\r
\n" ); document.write( "\n" ); document.write( "    - Wind and Current problems \r
\n" ); document.write( "\n" ); document.write( "    - More problems on upstream and downstream round trips \r
\n" ); document.write( "\n" ); document.write( "    - Wind and Current problems solvable by quadratic equations \r
\n" ); document.write( "\n" ); document.write( "    - Selected problems from the archive on the boat floating Upstream and Downstream \r
\n" ); document.write( "\n" ); document.write( "    - Selected problems from the archive on a plane flying with and against the wind \r
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