A marathon is 26 miles 385 yards long. That is about what 1.4 x10 feet how many feet long is half a marathon

I believe that the correct measurement in feet is 1.4 x 10^5 feet. You forgot to include the ^5.

So since that is the measurement of 1 marathon, therefore half a marathon would simply be also half of that, that is:

0.7 x 10^5 feet

or

7 x 10^4 feet