The perimeter of a rectangular piece of land is 240 cm, the length is twice the width.

The perimeter of a rectangular piece of land is 240 cm, the length is twice the width. Outside the plot, at the same distance from its sides, trees were planted, the distance between which is 5 m, How many trees were planted.

The perimeter of the rectangle is calculated using the formula:
P = 2 * (a + b) where P is the perimeter, a is the length, b is the width
By condition, the length is equal to twice the width. those. the length is twice the width:
a = 2 * b = 2b
Substitute this expression into the perimeter formula:
P = 2 * (a + b) = 2 * (2b + b) = 2 * 3b = 6b
Let’s substitute the length of the perimeter (240m) into the formula:
P = 6b
240 = 6b
6b = 240
b = 240: 6
b = 40 (m)
The width of the rectangle is 40 m.
And the length is twice as large and equal to 80 m:
a = 2 * b
a = 2 * 40
a = 80 (m)

The width is 40 m and trees were planted along it after 5 m, which means there are only trees:
40: 5 = 8 (pcs.) Trees along the width
The width is 80 m and trees were planted along it after 5 m, which means there are only trees:
80: 5 = 16 (pcs.) Trees along the length

In a rectangle, two sides are width and two sides are length, which means that all trees have been planted:
8 * 2 + 16 * 2 = 16 + 32 = 48 (pieces) total planted

Answer: a total of 48 trees were planted.