If the area between the two rectangles is 1400 square centimeters, calculate the perimeter of the small rectangle

If the area between the two rectangles is 1400 square centimeters, calculate the perimeter of the small rectangle

What is corresponding edge
Let the length of a small rectangle be x and the width be y
Because the distance between the two rectangles is 5cm, the distance between the small rectangle and the large rectangle is 5cm
So the length of the big rectangle is x + 10cm, and the width is y + 10cm
The area between the two rectangles is equal to the area of the large rectangle minus the area of the small rectangle
That is: (x + 10) × (y + 10) - xy = 10x + 10Y + 100 = 1400
That is: x + y = 13
The perimeter of the small rectangle is 2 (x + y) = 13 × 2 = 26cm

When the length and width of a rectangle increase by 5 cm, its area increases by 125 square cm?

Let the length of the original rectangle be x cm and the width be y cm. According to the meaning of the title, the area of the increased rectangle - the area of the original rectangle = 125 square cm. The equation is as follows: & nbsp; & nbsp; & nbsp; & nbsp; (x + 5) × (y + 5) - xy = 125 & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; XY + 5x + 5Y + 25-xy = 125 & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; 5x + 5Y + 25 = 125 & nbsp; && nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; 5x + 5Y = 100 & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; X + y = 20 & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; because the perimeter of the rectangle = (length + width) × 2, the original perimeter of the rectangle is 20 × 2 = 40 (CM) & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; A: the circumference of the original rectangle is 40 cm