From Futility Closet

Since the ratio of kilometers to miles is very close to the Golden Ratio, consecutive terms later in the Fibonacci series (once you get to 3) are approximate conversions of those distances.
1, 1, 2, 3, 5, 8, 13, 21, …

3 miles is 5 km, 5 miles is 8 km, etc.

This knowledge, along with some bubble gum and a paper clip, should be sufficient to thwart the bad guys in at least three ways. Get on with it!