Setting Up Equations
Date: 11/26/97 at 21:39:22 From: Jessica Shortreed-Hume Subject: Setting up equations An airplane travels eight times as fast as a car. The difference in their speeds is 420 km/h. How fast is each vehicle travelling? I tried to set up a formula but it won't work no matter what I try. Help!
Date: 11/30/97 at 21:57:40 From: Doctor Allan Subject: Re: Setting up equations Hello Jessica! What you need to do is put the information you have into mathematical equations. Let me help you with the setup - then you can try to do the math yourself. Let's call the speed of the car x and the speed of the plane y. We are told that the speed of the plane is eight times the speed of the car. This means that (1) 8x = y Furthermore we are told that the difference in their speeds is 420 km/h. We get (2) y-x = 420 Do you understand how I did this part? If you did you are quite close to the answer. In equation (1) you are told that every time you see a y, you can replace it with 8x. So this is what you do in equation (2), enabling you to get a value for y. This value can be substituted into equation (1) yielding a value for x. Since x and y were the speeds of the car and the plane, you can put your answer back into words once you find x and y. I hope this helps. If it doesn't, please write again. -Doctor Allan, The Math Forum Check out our web site! http://mathforum.org/dr.math/
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