A household uses \(3000\,\text{kWh}\) of electricity in one year, where kWh means kilowatt-hours. A \(10\,\text{cm}\)-long strip is divided into these category lengths:
- Cooking: \(1.5\,\text{cm}\)
- Lighting: \(1.0\,\text{cm}\)
- Refrigeration: \(2.5\,\text{cm}\)
- Other appliances: \(5.0\,\text{cm}\)
a) Find the percent represented by each category.
b) Find the actual electricity use in \(\text{kWh}\) for each category.
c) What would the central angle of the refrigeration sector be in a circle graph of the same data?
Hints
- Compare each category length with the total strip length.
- Use each percentage to find a part of \(3000\,\text{kWh}\).
- A full circle is \(360^\circ\).
Solution
1. Compare each segment with the \(10\,\text{cm}\) total: cooking, \(\frac{1.5}{10} = 15\%\); lighting, \(\frac{1.0}{10} = 10\%\); refrigeration, \(\frac{2.5}{10} = 25\%\); other appliances, \(\frac{5.0}{10} = 50\%\).
2. The electricity uses are: cooking, \(3000\,\text{kWh} \times 0.15 = 450\,\text{kWh}\); lighting, \(3000\,\text{kWh} \times 0.10 = 300\,\text{kWh}\); refrigeration, \(3000\,\text{kWh} \times 0.25 = 750\,\text{kWh}\); other appliances, \(3000\,\text{kWh} \times 0.50 = 1500\,\text{kWh}\).
3. The refrigeration angle is \(360^\circ \times 0.25 = 90^\circ\).
Answer
a) Cooking: \(15\%\); lighting: \(10\%\); refrigeration: \(25\%\); other appliances: \(50\%\)
b) Cooking: \(450\,\text{kWh}\); lighting: \(300\,\text{kWh}\); refrigeration: \(750\,\text{kWh}\); other appliances: \(1500\,\text{kWh}\)
c) \(90^\circ\)