Unless

Thein Lwin 7291 School classes will be overcrowded unless the birthrate doesn't fall.Is the sentence correct? Thanks in advance.

No. School classes will be overcrowded unless the birthrate falls.

... unless the birthrate falls.
... if the birthrate doesn't fall.

tamguatlay Thein Lwin 7291 School classes will be overcrowded unless the birthrate doesn't fall.Is the sentence correct? Thanks in advance.No. School classes will be overcrowded unless the birthrate falls.

Thanks, tanguatlay. If so, is the following correct?
School classes will be overcrowded unless the birth rate doesn't rise.

While grammatically correct, it's confusing and poor form. You make your reader work too hard to understand. The double negative is difficult to understand.

Write "School classes will be overcrowded if the birthrate rises."

Note that it does NOT have the same meaning as your original sentences.

In you original sentence, if the birthrate remains the same (or rises), cl

School classes will be overcrowded unless the birthrate falls = School classes will be overcrowded if the birthrate doesn't fall.

Thanks again. I'd like to know whether there is the pattern: unless + negative verb.

Unless he studies hard, he will fail his exams.
If he studies hard, he will pass his exams.

Thein Lwin 7291Thanks again. I'd like to know whether there is the pattern: unless + negative verb.

Grammatically yes, but you need a good reason to use it as a matter of style.

Otherwise, it's just confusing.