document.write( "Question 179158: An automobile averaged 40 mph for part of a trip and 50 mph for the remainder. If the 5-hour trip covered 210 miles, for how long did the car average 40 mph? \n" ); document.write( "

Algebra.Com's Answer #134125 by ptaylor(2198) $\"\"$ $\"About$

You can put this solution on YOUR website!
Distance(d)=Rate(r) times Time(t) or d=rt; r=d/t and t=d/r
\n" ); document.write( "Let d=distance travelled at 40 mph
\n" ); document.write( "Then (210-d)=distance travelled at 50 mph
\n" ); document.write( "time travelling at 40 mph=d/40
\n" ); document.write( "time travelling at 50 mph=(210-d)/50
\n" ); document.write( "Now we are told that the above two times=5 hr, so:
\n" ); document.write( "d/40 +(210-d)/50=5 multiply each term by 200
\n" ); document.write( "5d +4(210-d)=1000 get rid of parens
\n" ); document.write( "5d+840-4d=1000 subtract 840 from each side
\n" ); document.write( "5d+840-840-4d=1000-840 collect like terms
\n" ); document.write( "d=160 mi distance travelled at 40 mph
\n" ); document.write( "Time travelled at 40 mph=160/40=4 hr----------------------ans
\n" ); document.write( " CK
\n" ); document.write( "40*4+50*1=210
\n" ); document.write( "210=210\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "Hope this helps---ptaylor \n" ); document.write( "

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