Soru 1
A rectangle has a fixed perimeter of 24 cm. What is the maximum possible area of this rectangle?
- A
$20 \, \text{cm}^2$
- B
$32 \, \text{cm}^2$
- Doğru cevap
$36 \, \text{cm}^2$
- D
$40 \, \text{cm}^2$
- E
$48 \, \text{cm}^2$
Çözüm
For a rectangle with a fixed perimeter, the maximum area is achieved when it is a square. Let the sides be $l$ and $w$, with perimeter $P = 2(l + w) = 24$, so $l + w = 12$. The area is $A = lw$. To maximize $A$ for fixed $l + w$, by the AM-GM inequality or by setting $l = w$, we get the maximum when $l = w = 6$. Thus, the rectangle is a square with side 6 cm, and area $A = 6 \times 6 = 36 \, \text{cm}^2$.