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The perimeter of a right-angled triangle is 72 cm - Edexcel - GCSE Maths - Question 8 - 2018 - Paper 1

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The perimeter of a right-angled triangle is 72 cm. The lengths of its sides are in the ratio 3 : 4 : 5. Work out the area of the triangle.

Worked Solution & Example Answer:The perimeter of a right-angled triangle is 72 cm - Edexcel - GCSE Maths - Question 8 - 2018 - Paper 1

Step 1

Calculate the lengths of the sides

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Answer

Given that the perimeter of the triangle is 72 cm, and the sides are in the ratio 3:4:5, we can represent the lengths of the sides as:

  • Side 1: 3x
  • Side 2: 4x
  • Side 3: 5x

The sum of the sides (the perimeter) is:

3x+4x+5x=723x + 4x + 5x = 72

This simplifies to:

12x=7212x = 72

To find the value of x, divide both sides by 12:

x=7212=6x = \frac{72}{12} = 6

Now, substituting x back into the expressions for the sides gives:

  • Side 1 = 3(6) = 18 cm
  • Side 2 = 4(6) = 24 cm
  • Side 3 = 5(6) = 30 cm

Step 2

Use the lengths to calculate the area

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Answer

Using the formula for the area of a right-angled triangle:

Area=12×base×height\text{Area} = \frac{1}{2} \times \text{base} \times \text{height}

Here, we can take the two shorter sides (18 cm and 24 cm) as the base and height. Thus:

Area=12×18×24\text{Area} = \frac{1}{2} \times 18 \times 24

Calculating the area:

Area=12×432=216 cm2\text{Area} = \frac{1}{2} \times 432 = 216 \text{ cm}^2

So, the area of the triangle is 216 cm².

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