Introduction
Area and perimeter questions appear throughout the SAT Math section's Geometry and Trigonometry domain, which accounts for roughly 15% of the test. You may need to compute an area or perimeter directly, identify a missing side length or dimension when the area or perimeter is already given, or find the area of a composite figure assembled from simpler shapes. Every formula you need is either on the SAT reference sheet or memorizable in under a minute — knowing which is which saves you precious time.
Core Concept
The key skill here is matching the right formula to the right shape, applying it correctly, and — when working backward — treating the area or perimeter as the output and a missing dimension as the unknown.
Composite figures are shapes that can be split into (or subtracted from) standard shapes. The strategy is always:
or, for a cutout:
Working backward example: If a rectangle has area cm² and length cm, set up and solve: cm.
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