How many meters of fence will a gardener need to enclose a garden that is 7m long and 21m2 in area.

To solve this problem, recall the formula for the area of a rectangle. The area of the rectangle is equal to the product of the length and the width. S = a * b, where a is the length and b is the width.
The perimeter of a rectangle is the sum of the lengths of all its sides. Since in a rectangle the opposite sides are equal, then P = 2 * (a + b), where a is the length, b is the width. Let’s calculate what the width of the rectangle is.
a = 21/7 = 3 meters.
Let’s calculate what the perimeter of the rectangle is.
P = 2 * (3 + 7) = 2 * 10 = 20 centimeters.
Answer: 20 centimeters.