Calculate the perimeter of a rectangle whose area is 400 and the sides are 4: 1

Let’s express the width of the rectangle in terms of d cm, then the length of the rectangle will be 4d cm.
Let’s make the equation:
d * 4d = 400;
4d ^ 2 = 400;
d ^ 2 = 400: 4;
d ^ 2 = 100;
d = √100;
d = 10 cm – the width of the rectangle.
Let’s calculate the length of the rectangle:
4d = 4 * 10 = 40 cm – the length of the rectangle.
Answer: 10 cm and 49 cm.