To solve this problem, we need to calculate the surface area that will be painted and tiled, then use the cost information to determine the total expense.

Step-by-Step Solution:

1. Dimensions of the Hall:

   • Length (L) = 40 m
   • Width (W) = 15 m
   • Height (H) = 3 m

2. Calculating Areas for Painting:

   • Walls: There are four walls, so we need to find the area of two pairs of opposite walls:
     • Area of two walls (Length x Height) = $2 \times 40 \times 3 = 240$ m²
     • Area of two walls (Width x Height) = $2 \times 15 \times 3 = 90$ m²
     • Total wall area = $240 + 90 = 330$ m²
   • Ceiling: This is a single surface:
     • Area of the ceiling (Length x Width) = $40 \times 15 = 600$ m²
   • Total area to be painted = $330 + 600 = 930$ m²

3. Calculating the Cost of Paint:

   • A 10-liter tin of paint covers 25 m² and costs £10.
   • Number of tins required = $\frac{930}{25} = 37.2$ (We round up since partial tins aren't available)
   • Total tins needed = 38 tins
   • Paint cost = $38 \times 10 = £380$

4. Calculating the Area and Cost for Tiling:

   • Floor area (Length x Width) = $40 \times 15 = 600$ m²
   • Each 1 m² tile costs £3.
   • Tiles cost = $600 \times 3 = £1800$

5. Total Cost:

   • Total cost = Paint cost + Tiles cost = $380 + 1800 = £2180$

Final Answer:

• Paint cost: £380
• Tiles cost: £1800
• Total cost: £2180

Would you like further details on any step, or do you have additional questions?

Here are five related questions to expand on this topic:

1. How would the cost change if the height of the hall was doubled?
2. What would be the cost if paint cost increased to £12 per 10-liter tin?
3. How much area would require painting if only the walls were to be repainted?
4. How would the total cost change if tiles cost £5 per m² instead of £3?
5. If a discount was applied to the paint, reducing it by 15%, what would the new total cost be?

Tip: Always double-check unit conversions and areas when dealing with costs for large surfaces.