2D Mensuration

2D Mensuration

Core areas:

Rectangle = l*b
Square = a^2
Triangle = 1/2*b*h
Circle = pi*r^2
Parallelogram = b*h
Trapezium = 1/2*(a+b)*h
Rhombus = 1/2*d1*d2

Perimeter:

Rectangle = 2(l+b)
Square = 4a
Circle circumference = 2*pi*r

Speed tricks:

• If all dimensions scale by k, area scales by k^2.
• For shaded regions, calculate larger area minus smaller area.
• Use pi = 22/7 when radius is multiple of 7; use 3.14 only when needed.