A homeowner installs \(28\) solar panels. Type A panels produce \(320\,\text{W}\) each, and Type B panels produce \(400\,\text{W}\) each. Together, the panels produce \(10\,\text{kW}\).
a) How many panels of each type are installed?
b) The system output will be increased to \(12\,\text{kW}\). How many additional Type B panels are needed if the number of Type A panels stays the same?
Hints
- Convert all power values to watts.
- Use one variable for the number of one panel type.
- The two panel counts add to \(28\).
- In part b, keep the Type A count unchanged and recalculate the required Type B output.
Solution
1. Convert the totals: \(10\,\text{kW} = 10{,}000\,\text{W}\) and \(12\,\text{kW} = 12{,}000\,\text{W}\).
2. Let \(x\) be the number of Type A panels. Then \(28 - x\) is the number of Type B panels. Write \(320x + 400(28 - x) = 10{,}000\).
3. Distribute and solve: \(320x + 11{,}200 - 400x = 10{,}000\), so \(-80x = -1200\) and \(x = 15\).
4. There are \(15\) Type A panels and \(28 - 15 = 13\) Type B panels.
5. The \(15\) Type A panels produce \(15 \cdot 320 = 4800\,\text{W}\). The Type B panels must produce \(12{,}000 - 4800 = 7200\,\text{W}\).
6. The new number of Type B panels is \(7200 \div 400 = 18\), so \(18 - 13 = 5\) additional panels are needed.
Answer
a) There are \(15\) Type A panels and \(13\) Type B panels.
b) \(5\) additional Type B panels are needed.