Question

1. No less than fifty men were injured in the accident

Answer 1

"No less" would mean that is has to be more than fifty men were injured. If you were to change it to "no more" than fifty men were injured, than it would less than fifty men were injured. I do not think that it has anything wrong with its grammar and that it does need any changes.

Hope that helps! n_n

Answer 2

I agree with the fact that nothing is wrong with the sentence except that NO LESS does not means more than fifty. No less simply means at least fifty. So, it could be fifty or more.

Answer 3

@lanre : Thanks for the correction n_n