So I had one of those questions on my math quiz. You know, 2 trains are 240 miles apart and traveling at each other on parallel tracks, it takes them 1.6 hours to reach/pass one another and one train is traveling 10 mph faster than the other. I dont know the algebraic equation to solve this, so I reached into my memory bank of miscellaneous equations that I have learned outside of school and recalled d÷t=s. This is my method: Since there are two trains traveling AT each other on straight parallel tracks, then neither one is going to cover the entire 240 mile distance before they meet. I first divide the distance in half - 120 miles. Then I convert 1.6 into a fraction - 8/5. Now, where D=distance, T=time and S=speed, I solve for d÷t=s to find the mean mph. (dividing with fractions is actually an inverted multiplication. Thus 8/5 becomes 5/8) So, 120/1*5/8=75/1, or 75. Now I divide the mph difference of the two trains by 2. So 10÷2=5. Add 5 to the first train. 80 mph. Subtract 5 from the second train. 70 mph. Now we have the speed of the two trains! This formula works with any set of whole numbers given that there are two variables (in this case the trains) and at least one is assigned a value for motion that is not 0. (if they were both not moving, then duh...)
Posted on: Sun, 09 Mar 2014 06:09:46 +0000
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