To find the actual diameter of the button, you can use the magnification formula:
\[ \text{Magnification} = \frac{\text{Image size}}{\text{Actual size}} \]
In this case, the magnification is 55 times, and the image size (diameter of the image) is 99 cm. Let \( x \) be the actual diameter of the button. Thus, we have:
\[ 55 = \frac{99 \text{ cm}}{x} \]
To solve for \( x \), rearrange the equation:
\[ x = \frac{99 \text{ cm}}{55} \]
Now, perform the division:
\[ x = \frac{99}{55} \approx 1.8 \text{ cm} \]
So, the button's actual diameter is approximately 1.8 cm.