Question 1
Paper 2, calculatorMedium12 marksA small hydroelectric station records its annual electricity generation to the nearest GWh. Figure 1 shows the recorded generation in years 1 to 6.
Let be the generation, in GWh, predicted for year by an arithmetic sequence model. The model is chosen so that its first and sixth terms match the recorded generation in years 1 and 6.
Calculate the increase in recorded generation from year 2 to year 3, and from year 5 to year 6.
Determine the first term and common difference of the model.
Hence, estimate the generation predicted by the model for year 9.
Write the total generation predicted by the model over the first nine years in sigma notation, and determine its value.
Comment on the suitability of this model for estimating generation in year 9, referring to the plotted data.