Distance, Rate and TimeDate: 3 Jun 1995 16:16:54 -0400 From: Richard Seguin Subject: Question on Distance, Rate and Time. I have a question like this: Ian travelled by train at 80km/h and then by car at 90 km/h. It took him 3 h to travel the total distance of 265km. Ok, what I did was: Train: Speed = 80km/h Time = X (80)(x)=80x Car: Speed: 90km/h Time 3-X 80x = 90 (3-x) 80x=270 - 90x 170x=270 x= 1.5 Train's Distance was 120 Km and it's time was 1.5H Car's Distance was 145km and it's time was 1.5H Is what I did right? Please reply ASAP! Before 8 EST would be appreciated. Richard Seguin Date: 6 Jun 1995 09:31:57 -0400 From: Dr. Ken Subject: Re: Question on Distance, Rate and Time. Hello there! >Ian travelled by train at 80km/h and then by car at 90 km/h. It took him 3 h >to travel the total distance of 265km. . . . >Car: > > Speed: 90km/h > Time 3-X I like this much. However, I think your next step isn't quite right. You say that the two distances 80x and 90(3-x) are equal, but I don't think we know that Ian travelled the same distance by each mode of transportation. Instead, use the total distance 265 to make the equation 265 = 80x + 90(3-x) since the two distances add to 265 265 = 80x + 270 - 90x 10x = 5 x = .5 So it looks like Ian traveled 1/2 hour by train, and then 2.5 hours by car. That means he went 40 km by train, and the remaining 225 km by car. Sound good? -K |
Search the Dr. Math Library: |
[Privacy Policy] [Terms of Use]
Ask Dr. Math^{TM}
© 1994- The Math Forum at NCTM. All rights reserved.
http://mathforum.org/dr.math/