) writes:
thank you for your help, the sums should stretch the old brain cells, not
used square and cube roots since collage!


square roots are done automatically by most hand calculators.
for cube roots on a hand calculator I do it by stepwise refinement, ie
try a number you think might work, mulitply it by itself 3 times, and see
what you get. if it's too high pick a lower number and try that. if its
too low try a higher number. it takes about 4 or 5 tries to get a number
close enough. since the boat's design displacement doesn't
change the cube root has to be found once.

on a computer with Basic or a spreadsheet the cube root is just the number
raised to a power of one third, ie. displacement**0.333, or in some
notations displacement^0.333

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