A swimming pool is 15 m long, 8 m wide, and 1 m deep, as shown in the diagram - Junior Cycle Mathematics - Question 4 - 2015

To find the total area that needs to be covered with tiles, we can calculate the area of the base as well as the sides of the pool.

• Area of the bottom:

  $A_{bottom} = 15 ext{ m} imes 8 ext{ m} = 120 ext{ m}^2$

• Area of the front and back sides:

  $A_{front/back} = 2 imes (15 ext{ m} imes 1 ext{ m}) = 2 imes 15 ext{ m} = 30 ext{ m}^2$

• Area of the left and right sides:

  $A_{left/right} = 2 imes (8 ext{ m} imes 1 ext{ m}) = 2 imes 8 ext{ m} = 16 ext{ m}^2$

• Total area of the pool:

$A_{total} = A_{bottom} + A_{front/back} + A_{left/right} = 120 + 30 + 16 = 166 ext{ m}^2$

Now, since each tile is 20 cm x 20 cm, we need to convert this to square meters:

$ext{Area of one tile} = 0.2 ext{ m} imes 0.2 ext{ m} = 0.04 ext{ m}^2$

Finally, to find the minimum number of tiles required,

$ext{Number of tiles} = \frac{166 ext{ m}^2}{0.04 ext{ m}^2} = 4150$

Therefore, the minimum number of tiles that Harry will need is 4150.

To find the volume of water in the swimming pool, we first determine the dimensions of the water level. The depth of water is given as 10 cm below the top of the pool. Since the total depth is 1 m (or 100 cm), the effective depth of the water is:

$ext{Depth of water} = 100 ext{ cm} - 10 ext{ cm} = 90 ext{ cm} = 0.9 ext{ m}$

Now we can calculate the volume of water using the formula:

$ext{Volume} = ext{Length} imes ext{Width} imes ext{Depth} = 15 ext{ m} imes 8 ext{ m} imes 0.9 ext{ m} = 108 ext{ m}^3$

Thus, the volume of water in the swimming pool is 108 m³.