Final answer:
The unknown scale size is approximately 0.878.
Step-by-step explanation:
The unknown scale size can be determined by comparing the sizes of the text in each row. We can observe that each row represents a smaller size than the previous row. The first row has a text size of 1, the second row has a smaller text size, the third row has an even smaller text size, and the fourth row has the smallest text size. Therefore, the unknown scale size is between 0.878 and 0.937.
To find the exact scale size, we can estimate the last decimal place. Since the space between the third and fourth small tick marks is divided into ten equal parts, we can estimate the hundredths place to be 3. Therefore, the unknown scale size is approximately 0.878.