Which one is correct:
We drove 50 miles today; tomorrow, we will travel 100 miles ......... .
The correct answer is:
farther
We drove 50 miles today; tomorrow, we will travel 100 miles farther.
Farther is an adjective and adverb that means to or at a more distant point.
Further is an adjective and adverb that means to or at a greater extent or degree.