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Sean
The important thing is you got there in the end, and I bet you had fun getting there.  You don't actually need a computerised spreadsheet to do it the way you finally hit upon, but it certainly helps.  You could have made a table using 'old fasioned' school mathematics but the focussing in (whoops sorry Frank) to an exact final value would have been tedious.  I expect, like me, you'll kick yourself when you see the slick solution; flip the barn, draw a staight line, and spot the 345 triangle.  DaveP