A wire 88 cm long is bent, in turn, into each of these four shapes. Which one encloses the greatest area? (Use π = 22/7 and √3 = 1.73.)

The wire's length is the perimeter in every case. Circle: 2π$r=88$ gives $r=14$ cm and area $(22/7)\times 196=616$ sq cm. Square: side 22 cm, area 484 sq cm. Equilateral triangle: side 88/3 cm, area (1.73/4) $\times (88/3{)}^2$ ≈ 373 sq cm. Rectangle: $2(30+14)=88$ cm, area 420 sq cm. So the circle wins at 616 sq cm. For a fixed perimeter the area rises as the shape grows more regular and rounder, and among all plane figures the circle encloses the most — the rectangle and the triangle are offered because equal perimeters feel as though they should give equal areas.