Right Triangle Calculation: Finding Hypotenuse with Area 30 cm² and Base 5

Question

The area of the triangle ABC is 30 cm².

What is the length of the hypotenuse?

S=30S=30S=30555AAABBBCCC

Video Solution

Solution Steps

00:00 Determine the length of the hypotenuse AC
00:03 Apply the formula for calculating the area of a triangle
00:06 (height(AB) x base(BC)) divided by 2
00:12 Substitute in the relevant values and proceed to solve
00:21 Multiply by the reciprocal in order to isolate AB
00:30 This is the size of AB
00:37 Now that we have 2 sides we can apply the Pythagorean theorem
00:42 We'll use it to isolate and find AC
00:48 Substitute in the relevant values and proceed to solve
00:57 Take the square root
01:02 This is the solution

Step-by-Step Solution

To find the length of the hypotenuse of the triangle, let's proceed with the following steps:

  • Step 1: Use the area formula to find the base.
  • Step 2: Apply the Pythagorean Theorem to find the hypotenuse.

Step 1:
The formula for the area of a right-angled triangle is:

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

Given that the area is 30 cm², and one leg (the height) is 5 cm, we can find the base:

12×base×5=30\frac{1}{2} \times \text{base} \times 5 = 30

Solve for base\text{base}:

12×base×5=30\frac{1}{2} \times \text{base} \times 5 = 30

Multiply both sides by 2:

5×base=605 \times \text{base} = 60

Divide by 5:

base=12cm\text{base} = 12 \, \text{cm}

Step 2:
With base and height (legs of the triangle) known, apply the Pythagorean theorem to find the hypotenuse, c c :

c2=(base)2+(height)2=122+52c^2 = (\text{base})^2 + (\text{height})^2 = 12^2 + 5^2

Calculate:

c2=144+25=169c^2 = 144 + 25 = 169

Take the square root to find c c :

c=169=13cmc = \sqrt{169} = 13 \, \text{cm}

Therefore, the length of the hypotenuse of the triangle is 13 cm.

Answer

13 cm