The value of the power given is,
[tex]P=1200\text{ W}[/tex]The hotplate is used for the time t is,
[tex]\begin{gathered} t=15\text{ minutes} \\ t=15\times60 \\ t=900\text{ s} \end{gathered}[/tex]Thus, the energy used is,
[tex]\begin{gathered} E=P\times t \\ E=1200\times900 \\ E=1080\times10^3\text{ J} \\ E=1080\text{ kJ} \end{gathered}[/tex]Hence, the energy used is 1080 kJ.
