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Triangle Perimeter and Area
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Triangle Perimeter and Area
Isla is making triangular labels for the bakery’s new pastry boxes. Use perimeter for the length around an edge and area for the amount of card covering a face. Show your calculations and include units.
Know what you are measuring
Remember: perimeter is the sum of all three side lengths. Area = ½ × base × perpendicular height. Perimeter uses linear units; area uses square units.
1.Finn says a triangular label with base 12 cm and perpendicular height 5 cm has an area of 60 cm². Is he correct? Explain the calculation and name the correct unit.
2.A triangular box insert has side lengths 9 cm, 12 cm and 15 cm. How much ribbon would go all the way around its edge?
3.One triangular pastry card has a base of 14 cm and a perpendicular height of 8 cm. Calculate the area of card needed for one face.
4.A triangular bunting flag has a base of 18 cm and an area of 72 cm². What is its perpendicular height?
5.The bakery makes a right-triangular window decal with perpendicular sides 6 cm and 8 cm. Its third side is 10 cm. Find its area and perimeter.
6.Ruben has 80 cm of decorative trim for a triangular sign. Two sides are 24 cm and 31 cm. How long must the third side be?
7.Two labels each have base 10 cm and perpendicular height 6 cm. Label A has side lengths 10 cm, 8 cm and 8 cm; Label B has side lengths 10 cm, 7 cm and 9 cm. Do they have the same area? Do they have the same perimeter? Show why.
8.A label has area 45 cm² and perpendicular height 9 cm. What is its base length?
- 5 cm
- 10 cm
- 15 cm
- 90 cm
9.Isla sketches a triangle with a base of 13 cm and a perpendicular height of 4 cm. She writes its area as 52 cm². Identify her mistake and give the correct area.
10.A triangular pastry box front must have an area of 48 cm² and a base of 12 cm. Suggest a suitable perpendicular height, then describe one possible set of side lengths that would make a valid triangle with that base. (Side lengths may be decimals.)
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