October 28th, 2009, 11:29 AM  #1 
Member Joined: Oct 2009 Posts: 39 Thanks: 0  Speed problem
I am not sure this problem belong to this section or not, but here it goes. I have been trying to solve this for a while. A bicyclist makes a daily ride of 40 miles at a constant speed. If he trains hard, he can increase his speed by 4 miles per hour, which would result in a halfhour decrease in time. Find his new speed. I tried many ways. One was to set up a table like this V T D  v t 40  v+4 t.5 40 But we still have 2 variables to solve??? Are we suppose to guess for one of the variable???? Any help is appriciated. Thank you. 
October 28th, 2009, 05:36 PM  #2  
Global Moderator Joined: May 2007 Posts: 6,378 Thanks: 542  Re: Speed problem Quote:
Start equation 40=vt End equation 40=(v+4)(t.5)=vt+4t.5v2. This leads to 4t.5v=2. Combine with first equation gives a quadratic in either t or v which can be solved. This is an elementary algebra problem and should be in that section.  
October 30th, 2009, 09:40 AM  #3 
Member Joined: Oct 2009 Posts: 39 Thanks: 0  Re: Speed problem
Thank you mathman. Do I need move this to elementary algebra section?

October 30th, 2009, 04:53 PM  #4  
Global Moderator Joined: May 2007 Posts: 6,378 Thanks: 542  Re: Speed problem Quote:
 

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