Hi,

You problem is that you gave us the wrong formulas, they should be:

=39000-3*A2
=28000-2*A2

If your X values are in the range A2:A20 and start at 0 and are incremented
1000 you will get the intersection at 11,000.

If this helps, please click the Yes button.

cheers,
Shane Devenshire

"ColinC" wrote:

Hi David. It's for a simple little project I've been given in uni, plotting
the economics of buying a machine costing £39000 that machines parts at £2
/part, or a machine costing £28000 that costs £3 per part to operate. up to
11000 parts, the cheaper machine wins, but after that, the dearer machine
scores. I am plotting cost on the y axis and numbers of parts on the x axis
for both machines. The lines should cross at 11000 parts.
Anyway, thanks David and Bernard for the tip on XY charts, I'll try it.
ColinC

"David Biddulph" wrote:

I don't understand what you are saying about a cross-over at 61000 or 61500.
From simple algebra the crossover has to be at X=2800-39000, i.e. X=-32000,
and hence Y=-69600.

If you are trying to look at that sort of data, then I'm surprised that
you've used a line chart. Don't you want an XY chart? Have you been
confused by Excel's misleading naming system for the chart types?
--
David Biddulph


"ColinC" wrote in message
...
I can draw a line chart o/k but not a graph that starts at x=0,y=0.
Obviously, this is because the x axis in Excel is divided up into domains,
from 0 to 1, 1 to 2, 2 to 3, etc and x values are shown as mid-ordinate
values. However, I want to plot the line graphs y=39000+3x, and y=2800+2x
and
show the crossoverpoint at 61000 where it should be, not at 61500!