Question 970770
Hint: Draw out the picture to get

<img src = "http://i150.photobucket.com/albums/s91/jim_thompson5910/ramp1_zpswcbmd6eu.png">

Then erase all of the extra unneeded parts of the drawing and you will be left with this


<img src = "http://i150.photobucket.com/albums/s91/jim_thompson5910/ramp2_zpslks0uf5o.png">


The ultimate goal is to find the value of x (the length of CD)