The area of a triangle is (1/2)bh. If base b = 12 and height h = 5, what is the area?

• A. 30
• B. 60
• C. 15
• D. 25

Answer: (A)

Area of a triangle is half the product of its base and height. This comes from comparing a triangle to a rectangle: if you take the same base and height and draw a diagonal, you split the rectangle into two congruent triangles, so each triangle has half the area of the rectangle. Therefore, area = (1/2) × base × height.

With base 12 and height 5, compute (1/2) × 12 × 5 = 6 × 5 = 30. So the area is 30.

The other numbers come from using the full rectangle area (12 × 5 = 60) or applying an incorrect division of the dimensions, which doesn’t follow the half-product rule for triangles.