Rules for Rounding Off Numbers
1. If the digit removed is more than 5, the preceding number increases by 1.
5.379 rounds to 5.38 if three significant figures are retained and to 5.4 if two significant figures are retained.
2. If the digit removed is less than 5, the preceding number is unchanged.
0.2413 rounds to 0.241 if three significant figures are retained and to 0.24 if two significant figures are retained.
3.If the digit removed is 5, the preceding number increases by 1 if it is odd and remains unchanged if it is even.
17.75 rounds to 17.8, but 17.65 rounds to 17.6.
If the 5 is followed only by zeros, rule 3 is followed; if the 5 is followed by nonzeros, rule 1 is followed:
17.6500 rounds to 17.6, but 17.6513 rounds to 17.7
4. Be sure to carry two or more additional significant figures through a multistep calculation and round off only the final answer.
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