1. The lanterns had to burn for eight to ten hours.
2. The lanterns had to burn for from eight to ten hours.
(Are both sentences OK? Which one do we have to use?)
1 is fine. Use this one!
2 is awkward with "from" in it.
2. The lanterns had to burn for from eight to ten hours.
(Are both sentences OK? Which one do we have to use?)
2 is awkward with "from" in it.