A power station burns 80 kilograms of coal per second. Each kg of coal contains 25 million joules of energy. What is the total power of this power station in watts?
Supposing total conversion of energy you have that in 1 second the station burns 80 kg of coal corresponding to: #80×25*10^6=2*10^9 J# of energy per second
or #2*10^9# Watts or #2# Gigawatts of power.
(Remember that power=energy/time or Joules/seconds)