Distance Between Parallel Planes

This is a VCE Specialist Mathematics question from 10minutequiz.com.
It shows two methods for finding the distance between parallel planes.
Method 1: Find any points A in plane 1 and B in plane 2. Find the scalar resolute of a vector AB in the direction of the normal vector)
Method 2: Using a formula which essentially performs the same operation (see the second half of the video)
More VCE Mathematics resources at 10minutequiz.com.

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Simplest method is the second one