In a square, one pair of opposite sides was made 50% longer and the other pair of opposite sides was made 50% shorter. what percentage of the square’s perimeter is the perimeter of the new rectangle?

The perimeter of the new rectangle = 100% the perimeter of the original square.

Explanation:
Assume that the side length of the square is m.
Therefore:
perimeter of the square = 4m
Now, we have:
1- One pair of the opposite sides was made 50% longer. This means that:
    new length of each side = m + m/2 = 3m/2
2- The other pair of opposite sides was made 50% shorter. This means that:
    new length of each side = m - m/2 = m/2
Therefore:
perimeter of the new rectangle = 2(length + width)
perimeter of new rectangle = 2 (3m/2 + m/2) = 2 (2m) = 4m

Now, we can note that the perimeter of the new rectangle is equal to the perimeter of the original square.
Therefore, the perimeter of the new rectangle = 100% the perimeter of the original square.

Hope this helps :)