Quick questions on Area and perimeter of plane figures explained: O-Level E-Maths

The perimeter is the total distance around a shape, found by adding all the outer sides. For a circle the perimeter is called the circumference:

A composite figure is built from standard shapes. Find its area by splitting it into pieces and adding, or by taking a large shape and subtracting a removed piece. The perimeter of a composite shape follows the actual outer boundary, which may include parts of circles.

Area is measured in square units ($\text{cm}^2$, $\text{m}^2$) and perimeter in linear units ($\text{cm}$, $\text{m}$). Convert all lengths to the same unit before calculating, and state the correct unit with the answer.

Convert all measurements to one unit before calculating, and give area in square units.

The perimeter follows the actual outline, so a removed semicircle replaces a straight edge with a curved one.

Find the area of a triangle with base $12\ \text{cm}$ and perpendicular height $5\ \text{cm}$. [1 mark]

Find the circumference of a circle of diameter $10\ \text{cm}$, taking $\pi = 3.142$. [2 marks]

Find the area of a trapezium with parallel sides $6\ \text{cm}$ and $10\ \text{cm}$ and height $4\ \text{cm}$. [2 marks]