Answer is in the photo. I can't attach it here, but I uploaded it to a file hosting. link below! Good Luck!
tinyurl.com/wpazsebu
check the picture below.
now, if we split that triangle like so with that red line, we can use the right-triangle there, to get θ.

It would be 7.62 centimeters. Just multiply how many inches you have by 2.54, and you'll have your conversion.
~Silver
I believe it is 65 percent