Geometry and trigonometry make up about 15% of the SAT Math section. These 5 mistakes account for most lost points.

Mistake 1: Confusing Area and Perimeter

The trap: The question asks for the area, you calculate the perimeter (or vice versa).

A rectangle with length 8 and width 5:

Always underline what the question is actually asking for.

Mistake 2: Forgetting the Reference Sheet

The SAT provides a reference sheet with common formulas (area of a circle, volume of a cylinder, etc.). Many students forget it exists. Before any geometry question, check if the formula you need is on the reference sheet.

Key formulas provided: , , , , .

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Mistake 3: Radius vs Diameter

The trap: The question gives the diameter, you use it as the radius.

"A circle has a diameter of 10. What is its area?"

Wrong:

Right: , so

Always convert diameter to radius first: .

Mistake 4: Assuming Right Angles

The trap: A diagram looks like it has a right angle, but it is not marked.

On the SAT, you can ONLY assume a right angle if:

Never assume from the visual appearance alone.

Mistake 5: Misusing the Pythagorean Theorem

The trap: Using where is not the hypotenuse.

Remember: is ALWAYS the longest side (opposite the right angle). If you are solving for a leg:

Not .

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SAT Pro Tip

Draw on the test. Seriously. Label all given measurements, mark right angles, and write unknown values as variables. A well-labeled diagram prevents more errors than any formula sheet.

Practice geometry with our Geometry lessons with interactive exercises and hints.