1. Ulleongdo is 87.4 km away from Dokdo.
2. It is 87.4 km away from Ulleongdo to Dokdo.
3. It is 87.4 km from Ulleongdo to Dokdo.
(Are they all grammatical?)
1 and 3 are fine.
With "from" in the sentence, "away" is unneeded.
2. It is 87.4 km away from Ulleongdo to Dokdo.
3. It is 87.4 km from Ulleongdo to Dokdo.
(Are they all grammatical?)
With "from" in the sentence, "away" is unneeded.