Driving along a crowded freeway, you notice that it takes a time t to go from one mile marker to the next. When you increase your speed by 4.0 mi/h, the time to go one mile decreases by 9 s. What was your original speed in mi/h?(adsbygoogle = window.adsbygoogle || []).push({});

(this is from chapter 1 in my physics book, but it's been a long time since I've had math and for the life of me can't figure out how to set it up!)

Xmph=original speed

t= original time seconds/mile

s= seconds

It seems to me that Xmph/t = (xmph+4mph)/(t-9s), but I can't figure out where to move from here... please, any help on the set-up of this equation would be greatly appreciated! I know this is supposed to be easy but my brain just can't work it...

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# Increase in speed, decrease in time

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