If I, b and h be the length, breadth and height respectively of a room, then area of its 4 walls = (.....) sq units.

Answer

To find the area of the four walls of a room with length (L), breadth (B), and height (H), we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Structure**:
The room has four walls. Two walls will have dimensions of length and height, and the other two walls will have dimensions of breadth and height.

2. **Calculate the Area of the Walls**:
- The area of the two walls with length (L) and height (H) is:
\[ \text{Area of two length walls} = 2 \times (L \times H) = 2LH \]
- The area of the two walls with breadth (B) and height (H) is:
\[ \text{Area of two breadth walls} = 2 \times (B \times H) = 2BH \]

3. **Combine the Areas**:
- Now, we can add the areas of all four walls together:
\[ \text{Total Area of 4 Walls} = 2LH + 2BH \]

4. **Factor Out Common Terms**:
- We can factor out the common term, which is 2H:
\[ \text{Total Area of 4 Walls} = 2H(L + B) \]

5. **Final Expression**:
- Therefore, the area of the four walls of the room is given by:
\[ \text{Area of 4 walls} = 2H(L + B) \text{ sq units} \]

### Final Answer:
The area of the four walls = \( 2H(L + B) \) sq units.

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