How to scale a billboard to ratio

[teenc86508545]

I have a billboard that I am desgiing in indesgin, the final requested dymentions is 14' x 48', which indesgin obviously doesnt design in feet.. The printer sent a ratio 1/4 “ = 1’ scale - 300 dpi or better.  Not knowing anyting about the scale ratio, and this being my first project with a scale given, I googled and tried to follow a youtube video, I tried to do the math but was lost.  ANy help would be appeciated! 

[BobLevine · Accepted solution]

That is a 48:1 scale which seems a bit large. As for the 300ppi, I strongly suspect and hope they mean BEFORE it gets scaled up to billboard size. 

So, doing the math, the InDesign file would be 3.5" x 12"