My first thought was $5.0*10^3$, but the first zero is not significant here. Should the answer be $0.5*10^4$?
$\endgroup$ 71 Answer
$\begingroup$How accurately have you measured?
If you know that your answer is correct to the nearest whole number, then you should write $5.000 \times 10^3$
If you know that your answer is correct to the nearest ten, then you should write $5.00 \times 10^3$
If you know that your answer is correct to the nearest hundred, then you should write $5.0 \times 10^3$
If you know that your answer is correct to the nearest thousand, then you should write $5 \times 10^3$
If you know that your answer is correct to the nearest 0.1, then you should write $5.0000 \times 10^3$
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