Find the missing number in the ratio.

I've been stuck and still have no clue how to do these after countless attempts and fails! Okay, here's how the question goes: "The following ratio gives us a unit rate of 8 feet per second. Fill in the missing number in the ratio." That part alone is confusing enough. Furthermore, "4/? feet : 1/4 second" is listed below it. How in the world do you find the answer? Before you ask—yes, I did use the lightbulb button to try and figure it out. Can someone help give further information?