A cuboid is 8 m long . 12 m broad and 3.5 m high. Find its
lateral surface area.

Answer

To find the lateral surface area of the cuboid, we will follow these steps:

### Step 1: Understand the formula for lateral surface area of a cuboid.
The formula for the lateral surface area (LSA) of a cuboid is given by:
\[ \text{LSA} = 2h(l + b) \]
where:
- \( h \) = height of the cuboid
- \( l \) = length of the cuboid
- \( b \) = breadth of the cuboid

### Step 2: Identify the dimensions of the cuboid.
From the problem, we have:
- Length (\( l \)) = 8 m
- Breadth (\( b \)) = 12 m
- Height (\( h \)) = 3.5 m

### Step 3: Substitute the values into the formula.
Now, we will substitute the values of \( l \), \( b \), and \( h \) into the formula:
\[ \text{LSA} = 2 \times 3.5 \times (8 + 12) \]

### Step 4: Calculate the sum of length and breadth.
First, calculate \( l + b \):
\[ l + b = 8 + 12 = 20 \]

### Step 5: Substitute the sum back into the formula.
Now substitute this back into the formula:
\[ \text{LSA} = 2 \times 3.5 \times 20 \]

### Step 6: Perform the multiplication.
Now, calculate:
\[ 2 \times 3.5 = 7 \]
Then,
\[ 7 \times 20 = 140 \]

### Step 7: Write the final answer with the correct units.
Thus, the lateral surface area of the cuboid is:
\[ \text{LSA} = 140 \, \text{m}^2 \]

### Summary of the Solution:
The lateral surface area of the cuboid is \( 140 \, \text{m}^2 \).

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