To solve this problem, we need to determine the volume of water required to fill the swimming pool.

Step-by-Step Solution:

1. Identify Pool Dimensions:

   • Length = 2.5 m
   • Height (depth) = 1.5 m
   • Thickness of the slab (concrete walls) = 0.3 m or 30 cm

2. Calculate Inner Dimensions: Since the thickness of the walls is 0.3 m on each side, we subtract 0.6 m from both the length and width of the pool to get the inner dimensions.

   • Inner Length = 2.5 m - 2 * 0.3 m = 2.5 m - 0.6 m = 1.9 m
   • Inner Width = 1.9 m (assuming it's a square pool from the plan view)
   • Inner Depth = 1.5 m (as this is the height given)

3. Calculate Pool Volume: Volume $V$ = Inner Length * Inner Width * Inner Depth

   $V = 1.9 \, \text{m} \times 1.9 \, \text{m} \times 1.5 \, \text{m}$

   $V = 5.415 \, \text{m}^3$

4. Convert Cubic Meters to Litres: Since 1 cubic meter equals 1000 litres, we multiply by 1000 to get the volume in litres.

   $V = 5.415 \times 1000 = 5415 \, \text{litres}$

Final Answer:

Approximately 5415 litres of water are needed to fill the swimming pool.

Would you like more details on any of these steps, or do you have further questions?

Related Questions:

1. How would the required litres change if the wall thickness increased to 40 cm?
2. What would the volume be if the pool’s height was reduced by 0.5 m?
3. How would you calculate the concrete volume used for the walls?
4. If the pool length was extended by 1 m, what would be the new water volume?
5. How would you calculate the filling time if water flows at 500 litres per minute?

Tip:

Always ensure to double-check unit conversions, especially between cubic meters and litres, as these can significantly affect the answer.