document.write( "Question 1191430: A river is flowing downstream at rate of 2km/h.
\n" );
document.write( "Murray can swim at a rate of 3km/h.
\n" );
document.write( "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.
\n" );
document.write( "How far did Murray swim downstream?\r
\n" );
document.write( "\n" );
document.write( "I got 15/16 km but the answer is 5/12 km. How did it get to 5/12km? \n" );
document.write( "
Algebra.Com's Answer #823221 by Alan3354(69443)![]() ![]() You can put this solution on YOUR website! A river is flowing downstream at rate of 2km/h. Note: they always flow downstream. \n" ); document.write( "========================================= \n" ); document.write( "Murray can swim at a rate of 3km/h. \n" ); document.write( "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. \n" ); document.write( "How far did Murray swim downstream? \n" ); document.write( "t1 = d/(3+2) is the time swimming downstream. \n" ); document.write( "t2 = d/(3-2) is the time swimming upstream. \n" ); document.write( "============== \n" ); document.write( "t1 + t2 = 0.5 hours (given) \n" ); document.write( "----- \n" ); document.write( "d/5 + d = 0.5 \n" ); document.write( "d + 5d = 2.5 \n" ); document.write( "6d = 2.5 \n" ); document.write( "d = 2.5/6 = 5/12 km \n" ); document.write( "===================================\r \n" ); document.write( "\n" ); document.write( "I got 15/16 km but the answer is 5/12 km. How did it get to 5/12km? \n" ); document.write( "================== \n" ); document.write( "Might be interesting to see how you got 15/16. \n" ); document.write( "============================= \n" ); document.write( "The average speed of a round-trip is 2*v1*v2/(v1+v2) \n" ); document.write( "avg speed = 2*5*1/(5+1) = 10/6 = 5/3 km/hr \n" ); document.write( "d = r*t \n" ); document.write( "d = (5/3)*0.5 = 5/6 km round trip \n" ); document.write( "----> 5/12 km each way \n" ); document.write( " \n" ); document.write( " |