I don't like the way this question is worded. It perpetuates the idea that mathematics is a collection of formula. Here is another wording.
John has to measure the perimeter of three parks. The first park has 4 sides but the lengths of the 4 sides are all different. How can he measure the perimeter?
Answer: Measure the lengths of the 4 sides and add the lengths.
The second park is a rectangle. Is there an easier way to measure the perimeter? If so, what is it?
Answer: Yes. Start at one corner and measure the length of a side, turn the corner and measure the length of the next side. Add the lengths of the two sides and multiply the sum by 2.
The third park is a square. Is there an even easier way to measure the perimeter? If so, what is it?
Answer: Yes. Measure the length of one side and multiply this length by 4.