document.write( "Question 1046172: A boat travelled at a certain speed to a jetty 30 km away, then reduced speed by 4km/hr and returned to its starting
\n" ); document.write( "point.
\n" ); document.write( "If the boat had travelled at a steady and constant speed of 8km/hr for the entire trip, the total time would have been
\n" ); document.write( "half an hour less.
\n" ); document.write( "Determine the initial speed of the boat. \n" ); document.write( "
Algebra.Com's Answer #661690 by jorel555(1290)\"\" \"About 
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If the boat had a constant speed of 8 km/h over 60 kilometers, it would have taken 60/8 hours, or 7.5 hours. A half hour more would make it 8 hours. Let r be the boat's returning rate. Then:
\n" ); document.write( "30/(r+4)+30/r=8
\n" ); document.write( "30r+30(r+4)=8(rē+4r)
\n" ); document.write( "60r+120=8rē+32r
\n" ); document.write( "8rē-28r-120=0
\n" ); document.write( "2rē-7r-30=0
\n" ); document.write( "(2r+5)(r-6)=0
\n" ); document.write( "r=-5/2 or 6
\n" ); document.write( "Throwing out the negative result, we get a returning rate of 6 km/h, which makes the starting rate 10 km/h. \n" ); document.write( "
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