document.write( "Question 31725: Could someone PLEASE help me with these? I need help badly. Thanks for your time.\r
\n" ); document.write( "\n" ); document.write( "1. A plane flies 720 mi against a steady 30-mi/h headwind and then returns to the same point with the wind. If the entire trip takes 10 h, what is the plane’s speed in still air?\r
\n" ); document.write( "\n" ); document.write( "2. Solve for x. 2/5=x-2/20\r
\n" ); document.write( "\n" ); document.write( "3. Kevin earned $165 interest for 1 year on an investment of $1500. At the same rate, what amount of interest would be earned by an investment of $2500?
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Algebra.Com's Answer #18345 by Paul(988)\"\" \"About 
You can put this solution on YOUR website!
1.
\n" ); document.write( "A total distance of 720 miles with x sppeed:
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Cross multiply
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document.write( "720[(x+30)+(x-30)]=10[(x+30)(x-30)]
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document.write( "\"1440x=10%28x%5E2-900%29\"
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document.write( "\"10x%5E2-1440x-9000\"
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document.write( "Divide the equation by 10:
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document.write( "Use the quadratic formula:
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document.write( "\"x+=+%28-b+%2B-+sqrt%28+b%5E2-4%2Aa%2Ac+%29%29%2F%282%2Aa%29+\" 
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document.write( "a=1, b=-144, c=-900
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document.write( "\"x+=+%28-%28-144%29+%2B-+sqrt%28+%28-144%29%5E2-4%2A1%2A-900+%29%29%2F%282%2A1%29+\"
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document.write( "\"x=%28144%2B-sqrt%28+20736%2B3600%29%29%2F2\"
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document.write( "\"x=%28144%2B-sqrt%2824336%29%29%2F2\" --->Remove the negative:
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document.write( "\"x=%28144%2B156%29%2F2\"
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document.write( "x=150
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document.write( "Hence, the speed of the plane is 150mph.\r
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document.write( "2.\"2%2F5=x-2%2F20\"
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document.write( "Multiply the whole equation by 20 and simplfy:
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document.write( "\"20%282%2F5%29=20%28x%2F1%29-20%282%2F20%29\"
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document.write( "4(2)=20(x)-2
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document.write( "10=20x
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document.write( "x=0.5\r
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document.write( "3.Simple intest is given by A=(prinicpal * Time * rate)/100 
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document.write( "Let the rate be x:
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document.write( "1500x=16500
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document.write( "x=11 (rate)
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document.write( "A=\"%282500%2A1%2A11%29%2F100\"
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document.write( "x=275
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document.write( "Hence, the rate is 11% and with he same rate the money earned is $275.
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document.write( "Paul. \n" );
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