What is the area of a triangle with base 8 and height 5?

• A. 40
• B. 20
• C. 8
• D. 16

Answer: (B)

The area of a triangle is found by multiplying the base by the height and then dividing by 2, because a triangle is half of the rectangle with the same base and height. With base 8 and height 5, you get 8 × 5 = 40, and then 40 ÷ 2 = 20, so the area is 20. If you skip the division by 2, you’d get the area of the corresponding rectangle (40), not the triangle. The other numbers come from not applying the half factor or from using only one dimension instead of both.