[Grammar] Help me with '~ enough to, too ~ to, so ~ that'

[pseudo]

Dear teachers
I have a question with regard to 'to infinitive'. I would greatly appreciate if you could answer. ​

s1. He is so old that he cannot do the work.
= He is too old to do the work.

s2. He is so old that he can do the work.
= He is old enough to do the work.

s3. He is not so old that he can do the work. (?)
= He is not old enough to do the work. ( O )

Does s3 make sense? I think "He is not old enough to do the work" has the same meaning with "He is too young to do the work." but I'm not sure if "He is not so old that he can do the work." is correct.

 

[SlickVic9000]

(Not a Teacher)

S3 makes sense, but this sort of sentence is usually negative, like so:

"He is not so old that he can't do the work."

But to reiterate, S3 is perfectly fine, just not typical.

 

[bhaisahab]

s2 and s3 seem very unnatural to me.

 

[pseudo]

thank you for your replies.