What is the perimeter of an isosceles triangle with equal sides 9 cm each and the third side 5 cm?

Options

A. 40 cm
B. 23 cm
C. 22 cm
D. 69 cm

Answer

To find the perimeter of the isosceles triangle with equal sides of 9 cm each and a base of 5 cm, follow these steps:

### Step 1: Identify the sides of the triangle
In an isosceles triangle, two sides are equal. Here, the equal sides are both 9 cm, and the base (third side) is 5 cm.

### Step 2: Write down the lengths of the sides
- Length of the first equal side = 9 cm
- Length of the second equal side = 9 cm
- Length of the base (third side) = 5 cm

### Step 3: Calculate the perimeter
The perimeter of a triangle is the sum of the lengths of all its sides. Therefore, we can calculate the perimeter as follows:

\[ \text{Perimeter} = \text{Side 1} + \text{Side 2} + \text{Base} \]

Substituting the values:

\[ \text{Perimeter} = 9 \, \text{cm} + 9 \, \text{cm} + 5 \, \text{cm} \]

### Step 4: Perform the addition
First, add the lengths of the equal sides:

\[ 9 \, \text{cm} + 9 \, \text{cm} = 18 \, \text{cm} \]

Now add the base:

\[ 18 \, \text{cm} + 5 \, \text{cm} = 23 \, \text{cm} \]

### Step 5: State the final answer
The perimeter of the isosceles triangle is:

\[ \text{Perimeter} = 23 \, \text{cm} \]

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