# GRE Math : How to find the area of an acute / obtuse triangle

## Example Questions

### Example Question #2 : Acute / Obtuse Triangles

What is the area of a triangle with side lengths 18, 24, and 30?

280

140

196

216

342

216

Explanation:

The question doesn't tell us if this is a right triangle, so we can't assume that it is. But there is a formula to find the area when we don't know the height: area = [p(p – a)(p – b)(p – c)]1/2, where a, b, and c are the side lengths and p is half of the perimeter. The perimeter is 18 + 24 + 30 = 72, so p = 72/2 = 36.

Then area = [36(36 – 18)(36 – 24)(36 – 30)]1/2 = [36 * 12 * 6 * 18]1/2 = 216.

### Example Question #21 : Triangles

You are asked which triangle is larger. You are only told that theyhave the same base length and that one contains at least one 3 inch side and the other contains at least one 4 inch side. Determine whether the left or right triangle is larger.

The right triangle is larger

The triangles are equal

The left triangle is larger

It is impossible to determine from the given information.