The total energy input to the National Grid from one power station is 34.2 GJ. The National Grid has an efficiency of 0.992 Calculate the useful energy output from this power station to consumers in GJ. [3 marks] Useful energy output = __ GJ

The efficiency of any machine or system, like the National Grid in our problem, specifies the part of the input energy that is utilized successfully, while the remainder is wasted or lost due to inefficiencies in the system. Since the National Grid has an effectiveness of 0.992, which is exceedingly high, we would anticipate a significant part of the input energy to be productively used with minimal wastage. To find out the useful energy output, we would need to multiply our total energy input by the efficiency: Substituting the figures given: So, the required answer is approximately 33.8984 GJ. Remember as a teacher's comment, for calculations involving scientific and practical problems, if the answer isn't precise (in decimal), express your answer to the appropriate number of decimal places or significant figures based on what's specified in your instructions or the context.Hence, the correct answer with good significance would be , depending on how precise we need the number.