### All PSAT Math Resources

## Example Questions

### Example Question #83 : Solid Geometry

A* regular tetrahedron* has four congruent faces, each of which is an equilateral triangle.

A given tetrahedron has edges of length six inches. Give the total surface area of the tetrahedron.

**Possible Answers:**

**Correct answer:**

Explanation:

The area of an equilateral triangle is given by the formula

Since there are four equilateral triangles that comprise the surface of the tetrahedron, the total surface area is

Substitute :

square inches.

### Example Question #84 : Solid Geometry

Give the surface area of the above *tetrahedron*, or four-faced solid, to the nearest tenth.

**Possible Answers:**

Insufficient information is given to answer the question.

**Correct answer:**

Explanation:

The tetrahedron has four faces, each of which is an equilateral triangle with sidelength 7. Each face has area

The total surface area is four times this, or about .

Rounded, this is 84.9.

### All PSAT Math Resources

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