Question 263548
It means "just be careful".
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To comply with the sentences you should carry out your
work with at least 6 decimal places at each step if 
you are asked to arrive at an answer that is good to
the 3rd decimal place.  Don't round off your decimals
to the 3rd place every step along the line while you
are working the problem.
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Hope that helps.
Cheers,
Stan H.