Mensuration

Area and perimeter, circles, arcs and sectors, surface area and volume of 3D solids, and similar-shape scale factors.

Mensuration is about length, area and volume — and knowing which formula to reach for.

Circles

Circumference

= \pi d = 2\pi r

Area

= \pi r^2

Arc length

= \dfrac{\theta}{360} \times 2\pi r

and sector area

= \dfrac{\theta}{360} \times \pi r^2

A sector with radius r and angle θ — take the fraction θ/360 of the whole circle.

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