Question 1203941
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I'll give a hint. The center of the shaded ball will follow the curved path shown in red.
*[illustration Screenshot_302.png]
The red curve is 3.5 cm away from the black perimeter (composed of the rectangle and black circles) because this is the radius of each ball (7/2 = 3.5)


Here's an interactive GeoGebra applet in which you can move the shaded ball around to get an idea of what's going on.
<a href = "https://www.geogebra.org/m/rymwmsxj">https://www.geogebra.org/m/rymwmsxj</a>
If the canvas is blank, you may need to refresh the page.
Or you may need to click the curved arrow at the center of the screen (after hovering your mouse over top).
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