First compute the amount of water needed per day:
[tex]60\times5400=324000L[/tex]
Transform the above amount to m^3:
[tex]324000\times0.001=324\,m^3[/tex]
Compute the volume of the reservoir:
[tex]49\times27\times25=33075\,m^3[/tex]
Now compute the number of days covered by the amount of water like this:
[tex] \frac{33075}{324}=102\,\,\,\text{days.} [/tex]
