What You See...

If you're used to Lotus graphs, the HP CALC graph may leave you scratching your head. It can only show one independent variable at a time, and nothing is labeled. However, in this graph, the vertical axis represents Profit. The horizontal axis shows the number of Units. The dotted line is the break-even line, where Profit is zero.

Now press @ and see "COORD X=50.00 Y=0.00" on the top line of the graph. Press <Space Bar> to solve for the root of the equation. You should see: "ROOT X=44.08 Y=0.00". That's the break-even point.