The conversion between miles and feet is:
[tex] 1 mi = 5280 ft [/tex]
So we can set up a proportion to find how many feet corresponds to 250000 miles:
[tex] 1 mi: 5280 ft = 250000 mi :x [/tex]
and solving it, we find
[tex] x=\frac{5280 ft \cdot 250000 mi}{1 mi} =1.32 \cdot 10^9 ft [/tex]
