knowable

The similarity ratio of △ABC and △ A ′ B ′ C ′ is 1:2.

Their area ratio is the square of similarity ratio.

It is 1:4.

therefore

The area of △ A ′ B ′ C ′ is four times that of △ABC.

However, it seems that the title and data are wrong.

Yes, what is the area of △ABC?

Just give this data

Multiplying by 4 is the answer to the question.