math help??

2/(y-x) hr

Rap

Thanks Rap.. can you explain it to me??

Start at zero

Rachel catches Ben in t hours

Ben's distance from zero in t hours is d=2+xt

Rachel's distance from zero in t hours d=yt

both are the same distance from 0 (d) so set both relations equal to the other or 2+xt=yt

rearranging 2=yt-xt=(y-x)t and divide through by y-x so t=2/(y-x)

Now for the units---since the dimensions on 2 is miles and the dimensions on y and x are both in mi/hr, the dimensions on t are mi/(mi/hr) so t is in hr.

Rap

Rap,
I cannot thank you enough. I do understand how to do it now. I am 14 years old and am doing a practice book to get ready for a math competition in Algebra. I came in 5th last time in my City/County. That one stumped me, but after you explained it, I now understand where I was going wrong. I was thinking too much. Thanks for your help. What a great site.