A microscope has a scale of 250:1.

What does this scale mean?

I don't have an answer, but I'm not asking for a full answer either. I just need to understand what exactly they are asking for.

things appear to be 250 times as large as they really are

Ooohh, I understand now. Thank you ^^

When a microscope has a scale of 250:1, it refers to the magnification power of the microscope. In this case, it means that the image seen through the microscope will appear 250 times larger than the actual size of the object being observed. So, if you were to view an object measuring 1 millimeter in size, it would appear as if it were 250 millimeters (or 25 centimeters) in size when observed through the microscope. The scale indicates the ratio between the size of the image seen through the microscope and the actual size of the object.