SATMathematics Practice Test 1

Let x represent the number of installations that each unit on the y-axis represents.
Then $9\mathit{x},5\mathit{x},6\mathit{x},4\mathit{x},$ and $3.5\mathit{x}$ are the number of rooftops with solar panel installations in cities A, B, C, D, and E, respectively.
Since the total number of rooftops is 27,500, it follows that $9\mathit{x}+5\mathit{x}+6\mathit{x}+4\mathit{x}+3.5\mathit{x}=27,500,$ which simplifies to $27.5\mathit{x}=27,500$. Thus, $\mathit{x}=1,000$.
Therefore, an appropriate label for the y-axis is “Number of installations (in thousands).”
Choices A, B, and D are incorrect and may result from errors when setting up and calculating the units for the y-axis.