An isosceles triangle has base 20cm and each of the two equal sides measures 18 cm. What is its perimeter?

Answer

To find the perimeter of the isosceles triangle, we will follow these steps:

### Step 1: Identify the sides of the triangle
In an isosceles triangle, there are two equal sides and one base. Here, the lengths are:
- Base (b) = 20 cm
- Equal sides (a) = 18 cm each

### Step 2: Use the perimeter formula for the triangle
The formula for the perimeter (P) of an isosceles triangle is:
\[ P = 2a + b \]
where \( a \) is the length of the equal sides and \( b \) is the length of the base.

### Step 3: Substitute the values into the formula
Now, substitute the values of \( a \) and \( b \) into the formula:
\[ P = 2(18) + 20 \]

### Step 4: Calculate the perimeter
First, calculate \( 2 \times 18 \):
\[ 2 \times 18 = 36 \]
Now, add the base:
\[ P = 36 + 20 = 56 \]

### Step 5: State the final answer
The perimeter of the isosceles triangle is:
\[ P = 56 \text{ cm} \]

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