document.write( "Question 1004142: Going to the lake, has a mean speed of 12 mph. On the return trip the mean speed is 10 mph,. If the round trip takes 5.5 hrs., how long does the return trip take? \n" ); document.write( "

Algebra.Com's Answer #620686 by addingup(3677) $\"\"$ $\"About$

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The formula for distance is:
\n" ); document.write( "d= r*t where r is the rate (another word for speed) and t is time. Since we want to find t, let's divide both sides by rate:
\n" ); document.write( "t= d/r
\n" ); document.write( "----------
\n" ); document.write( "We have two speeds, so we have to add them up:
\n" ); document.write( "d/r+d/r= t Let's plug in the numbers in the problem:
\n" ); document.write( "d/12+d/10= 5.5 Now let's find a common denominator for 12 and 10: 12, 24, 36, 48, 60. Eureka!, 60 is divisible by 12 and by 10. Multiply all sides by 60:
\n" ); document.write( "60/12+60/10= 330 Simplify on left, divide:
\n" ); document.write( "60/12=5 and 60/10=6 Now we have:
\n" ); document.write( "5d+6d= 330
\n" ); document.write( "11d= 330 Divide by 11:
\n" ); document.write( "d= 30 This is the distance to the lake. And the return time is:
\n" ); document.write( "30/10= 3 hours
\n" ); document.write( "Proof:
\n" ); document.write( "30/10= 3
\n" ); document.write( "30/12= 2.5
\n" ); document.write( "Total: 3+2.5= 5.5 We have the correct answer. \n" ); document.write( "

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