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John.Heddles wrote: First point - the books vary through different revisions so far as pagination, etc., is concerned. Generally better for the readers if you post a happy snap of the question so that we are all singing from the same sheet of music.
As to the question - and also correct how was this possible ? They can't both be correct so there has to be an error along the way somewhere.
38kg looks to be a good answer (actually just a cigarette paper under 38kg).
If you ballast 50kg to run an iterative solution, the 50kg puts you outside the envelope by a bit over 10mm so it looks like you maybe took a wrong turn in your plotting. Perhaps you can post a happy snap of your arithmetic calculations and the graphical plot and it should be pretty easy to figure out what might have gone awry.