Area of a triangle
Name: _____________________ Date: __________
Show your thinking with numbers, words, or a drawing.
1. This right-angled triangle has a base of 6 cm and a height of 6 cm. What is its area in square centimetres?
2. This right-angled triangle has a base of 7 cm and a height of 5 cm. What is its area in square centimetres?
3. This right-angled triangle has a base of 6 cm and a height of 7 cm. What is its area in square centimetres?
4. This right-angled triangle has a base of 9 cm and a height of 7 cm. What is its area in square centimetres?
5. This right-angled triangle has a base of 5 cm and a height of 8 cm. What is its area in square centimetres?
Answer key · Area of a triangle
1. 18
Area of a triangle = ½ × base × height.
The two sides at the right angle are the base, 6 cm, and the height, 6 cm.
½ × 6 × 6 = ½ × 36 = 18 cm².
2. 17.5
Area of a triangle = ½ × base × height.
The two sides at the right angle are the base, 7 cm, and the height, 5 cm.
½ × 7 × 5 = ½ × 35 = 17.5 cm².
3. 21
Area of a triangle = ½ × base × height.
The two sides at the right angle are the base, 6 cm, and the height, 7 cm.
½ × 6 × 7 = ½ × 42 = 21 cm².
4. 31.5
Area of a triangle = ½ × base × height.
The two sides at the right angle are the base, 9 cm, and the height, 7 cm.
½ × 9 × 7 = ½ × 63 = 31.5 cm².
5. 20
Area of a triangle = ½ × base × height.
The two sides at the right angle are the base, 5 cm, and the height, 8 cm.
½ × 5 × 8 = ½ × 40 = 20 cm².
Try it together
Choose three objects at home. Estimate their measurements, then check together and explain the differences.