A brick measures `20 cm xx 10 cm xx 7.5 cm ` . How many bricks will be required for a wall ` 20 m xx 2m xx 0.75 m` ?

Answer

To determine how many bricks are required for a wall, we need to calculate the volume of the wall and the volume of a single brick, and then divide the volume of the wall by the volume of one brick.

### Step-by-Step Solution:

1. **Convert the dimensions of the brick from centimeters to meters:**
- Length of the brick = 20 cm = 20/100 m = 0.2 m
- Width of the brick = 10 cm = 10/100 m = 0.1 m
- Height of the brick = 7.5 cm = 7.5/100 m = 0.075 m

2. **Calculate the volume of one brick:**
\[ \text{Volume of one brick} = \text{Length} \times \text{Width} \times \text{Height} \]
\[ \text{Volume of one brick} = 0.2 \, \text{m} \times 0.1 \, \text{m} \times 0.075 \, \text{m} = 0.0015 \, \text{m}^3 \]

3. **Convert the dimensions of the wall from meters to cubic meters:**
- Length of the wall = 20 m
- Width of the wall = 2 m
- Height of the wall = 0.75 m

4. **Calculate the volume of the wall:**
\[ \text{Volume of the wall} = \text{Length} \times \text{Width} \times \text{Height} \]
\[ \text{Volume of the wall} = 20 \, \text{m} \times 2 \, \text{m} \times 0.75 \, \text{m} = 30 \, \text{m}^3 \]

5. **Calculate the number of bricks required:**
\[ \text{Number of bricks} = \frac{\text{Volume of the wall}}{\text{Volume of one brick}} \]
\[ \text{Number of bricks} = \frac{30 \, \text{m}^3}{0.0015 \, \text{m}^3} = 20000 \]

### Final Answer:
You will need **20,000 bricks** to construct the wall.