2025 YCKSS PRELIMS P2 Q9

2025 YCKSS PRELIMS P2 Q9

Secondary 4

11 marks

Chan is deciding whether to install solar panels. The information is shown below.

Month	January	February	March	April	May	June
Usage (kWh)	\(1007.8\)	\(1166.3\)	\(1133.6\)	\(1249\)	\(1248.5\)	\(1282.6\)

Item	Information
Electricity tariff	\(28.12\text{ cents per kWh}\) before \(9\%\) GST
Roof dimensions	\(9\text{ m}\) by \(4\text{ m}\)
One panel	\(1.65\text{ m}\) by \(1\text{ m}\)
Installation cost	\(\$10\,250\) per \(10\) panels; no GST
Generation	\(45\text{ kWh}\) per panel per month
Panel lifespan	\(25\) years

For the first six months of 2025, calculate
1. the average monthly electricity usage in kWh,[2]
2. the average monthly electricity cost.[2]
Calculate the maximum number of panels that fit on the roof.[2]
Should Chan install solar panels? Justify the decision with clear calculations.[5]

Solution:

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Answer:(a)(i) \(1181.3\text{ kWh}\) (ii) \(\$362.08\) (b) \(20\) (c) Yes; estimated monthly total \(\$154.55\).

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