Question 947868
How do i solve a problem with time, where a person drives 100miles in rain but when the rain stopped they drove 15miles faster for another 250 miles. If his total drive time was 10 hours how fast did he drive while it was raining? 
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let x=speed while driving 100 miles in the rain
x+15=speed while driving 250 miles after rain stopped
travel time=distance/speed
..
{{{100/x+250/(x+15)=10}}}
lcd:x(x+15)
250x+100x+1500=10x(x+15)
10x^2+150x=350x+1500
10x^2-200x-1500=0
x^2-20x-150=0
solve for x by quadratic formula:
{{{x = (-b +- sqrt( b^2-4*a*c ))/(2*a) }}}
a=1, b=-20, c=-150
ans:
x≈25.8
how fast did he drive while it was raining? 25.8 mph