1. **State the problem:** We need to find how many tiles, each 40 cm wide, can fit side by side along a wall that is 2.1 meters wide. 2. **Convert units:** The wall width is given in meters, and the tile width is in centimeters. Convert the wall width to centimeters to match units. $$2.1\text{ meters} = 2.1 \times 100 = 210\text{ cm}$$ 3. **Calculate the number of tiles:** Divide the total wall width by the width of one tile. $$\text{Number of tiles} = \frac{210\text{ cm}}{40\text{ cm}} = 5.25$$ 4. **Interpret the result:** Since we cannot place a partial tile, only whole tiles count. So, the number of tiles that can fit is the integer part of 5.25, which is 5. **Final answer:** 5 tiles can be placed side by side along the wall.