The volume of the hot tub is that of a cylinder:
[tex]V=\pi r^{2}h[/tex]
The height is 1.5 m
The radius is half the diameter, which is 1.3 m
So we get
[tex]V=\pi(1.3)^{2}(1.5)\approx7.964 m^{3}[/tex]
The density of water is 1 g/cm³
Convert to kg/m³:
[tex]\frac{1\ g}{1\ cm^{3}}*\frac{1\ kg}{1000\ g}*\frac{100^{3}\ cm^{3}}{1\ m^{3}}=\frac{10^{6}}{10^{3}}\ kg/m^{3}=1000\ kg/m^{3}[/tex]
The mass of the water is Volume*density:
[tex]7.964\ m^{3}*1000\ kg/m^{3}=7964\ kg[/tex]
So 7964 kg of water are needed to fill the tub.