document.write( "Question 271148: Rachel allows herself 1 hr to reach a sales appointment 50 mi away. After she has driven 30 mi, she realizes she must increase her speed by 15 mph in order to get there on time. What was her speed for the first 30 mi? I cannot familiarize this problem and it's driving me nuts. I am taking an online course and it's hard. I have tried to come up with a formula... If she travels x miles per hour for 30 miles and x+15 miles per hour for 20 miles she would get there in 60 mins, or one hour. x+x+15=50? wait miles per hour is distance/time. so 50 miles / 1hour. and she travels at x for 30 so 30 times x? I am so lost on this problem. I have tried a bunch more ways that don't make sense. Once i got x=1. She obviously did not travel at one mile per hour or she would never had made it 50 miles in one hour! It would be so much more funny if I wasn't dying over this problem! \n" ); document.write( "

Algebra.Com's Answer #198547 by Greenfinch(383) $\"\"$ $\"About$

You can put this solution on YOUR website!
After 30 miles time is 30/x
\n" ); document.write( "Next part is 20/(x + 15)
\n" ); document.write( "So 30/x + 20/(x + 15) = 1
\n" ); document.write( "LCM is x(x+15
\n" ); document.write( "so 30(x + 15) + 20x = x(x+15)
\n" ); document.write( "30x + 450 + 20x = x^2 + 15x
\n" ); document.write( "x^2 - 35x - 450 = 0
\n" ); document.write( "(x - 45)(X + 10) = 0
\n" ); document.write( "x = 45 or -10
\n" ); document.write( "initial speed is 45 mph \n" ); document.write( "

\n" );