7.1 The length of a rectangle is $25 \%$ greater than its width. By a straight cut, parallel to the shorter side, this rectangle is cut into a square and a rectangular strip. By what percentage is the perimeter of the square greater than the perimeter of the strip?
Answer: By $60 \%$. Solution: Let $a$ be the width of the rectangle, then its length is $1.25 a$. The perimeter of the resulting square is $4 a$, and the perimeter of the strip is $2 a+0.5 a=2.5 a$. The ratio of the perimeters is $4 a: 2.5 a=1.6$. Therefore, the perimeter of the square is greater than the perimeter of the strip by $0.6 \cdot 100 \% = 60 \%$