Perimeter or area? Never confuse the two

The difference in one sentence

• Perimeter = length around (the outline of the shape).
• Area = inside surface (within the shape).

The unit test

• Perimeter: cm, m, km (one dimension).
• Area: cm², m², km² (two dimensions).

If you see « m² » in a problem, it’s always an area.

Formulas to know (rectangle and square)

Shape	Perimeter	Area
Rectangle (L × W)	$2(L + W)$	$L \times W$
Square (side $c$)	$4c$	$c^2$
Circle (radius $r$)	$2\pi r$	$\pi r^2$

The visual mnemonic

Perimeter starts with « P » like « Path around ». Area = what you’d fill with paint or grass.

Classic trap: two shapes with same perimeter, different areas

An 8 × 2 rectangle and a 5 × 5 square:

• Perimeters: $2(8+2) = 20$ and $4 \times 5 = 20$ → equal.
• Areas: $8 \times 2 = 16$ and $25$ → different.

Given a fixed perimeter, the square has the largest area.

?Your turn

A rectangle is 12 m by 5 m. Its perimeter and area are:

A.P = 60 m, A = 34 m²B.P = 34 m, A = 60 m²C.P = 60 m², A = 34 mD.P = 17 m, A = 60 m²

Check