1. You can do this at least 5 to 10 times.
2. You can do this at least from 5 to 10 times.
(Is #2 grammatical? Do we need to use 'from' as in Sentence 2?)
2. You can do this at least from 5 to 10 times.
(Is #2 grammatical? Do we need to use 'from' as in Sentence 2?)