Grade 6 · Maths · Lessons
Half of a rectangle
🔺triangle▭rectangle½half📐base and height
Half of a rectangle.The big ideaA triangle is half of the rectangle round it. Base times height, then half.
How it works
A triangle is half of the rectangle round it. Base times height, then half.
A = 1/2 × base × height.
The height is measured straight up from the base, at a right angle.
Example 1: A whole-number triangle
- A triangle has base 9 ft and height 8 ft. What is its area?
- Base 9, height 8.
- 9 × 8 = 72, and half is 36.
- So the answer is 36.
Example 2: A fraction height
- A triangle has base 1 units and height 7/2 units. What is its area?
- Base 1, height 7/2.
- 1 × 7/2 = 7/2, and half is 7/4.
- So the answer is 7/4.
Example 3: A sail
- Mia sews a triangle sail. The base is 4 meters. The height is 3 meters. What is the area?
- Base 4 meters, height 3 meters.
- 4 × 3 = 12, and half is 6.
- So the answer is 6.
Words to know
- base
- The side you measure height from.
- height
- The straight-up distance at a right angle to the base.
Watch out
- Don't forget the half.
- Use the straight-up height, not a slanted side.
- Say square units.
Try it
- A triangle has base 3/2 in and height 1 in. What is its area?
- A triangle has base 3 m and height 8 m. What is its area?
- Mia sews a triangle sail. The base is 5 feet. The height is 3 feet. What is the area?
Answers: 1. 3/4 · 2. 12 · 3. 7.5
For grown-upsCut a rectangle along its diagonal and see two equal triangles.