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The measurement with three significant figures is 5.60 km.

Explanation:

Significant figures : The figures in a number which expresses the value of the magnitude of a quantity to a specific degree of accuracy is known as significant digits.

Rules for significant figures:

Digits from 1 to 9 are always significant and have infinite number of significant figures.All non-zero numbers are always significant. For example: 634, 6.84 and 62.4 all have three significant figures.All zero’s between integers are always significant. For example: 1005, 4.005 and 70.03 all have four significant figures.All zero’s preceding the first integers are never significant. For example: 0.0048 has two significant figures.All zero’s after the decimal point are always significant. For example: 4.300, 95.00 and 150.0 all have four significant figures.All zeroes used solely for spacing the decimal point are not significant. For example : 5000 has one significant figure.

The measurement with three significant figures is 5.60 km.

Where as 0.0005 m has 1 significant figure, 7,077 mg has 4 significant figures and 0.080 mm has 2 significant figures.

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