Answer:
The outline that will appear on the x-ray screen when a cylindrical container with three tennis balls lying horizontally inside passes through the scanner will be a rectangle. The dimensions of this rectangle will be 5.4 inches by 16.2 inches.
Here's how you can visualize it:
The cylindrical container, when viewed from the top, will appear as a circle with a diameter of 5.4 inches.
The three tennis balls inside the container will create a row, so you have three tennis balls aligned horizontally. The diameter of each tennis ball is 5.4 inches.
The x-ray scanner, which scans from the top only, will capture the entire outline of the cylindrical container and the tennis balls inside it. Since the tennis balls are aligned horizontally, they will form a line with a total length of 3 * 5.4 inches = 16.2 inches.
Therefore, the x-ray outline will be a rectangle with dimensions 5.4 inches by 16.2 inches.