## Unit Conversions and Significant Figures.

Convert the following to SI units:

**Known:**

*1 min = 60 s*

*1 hour = 60 min*

*1 day = 60 min*

*1 year = 365 days*

**a)Express your answer using two significant figures**

1.0 hour =3600 s (60 x 60)

1.0 day = 86400 s (60 x 60 x 24)

1.0 year = 31536000s ( 60 x 60 x 24 x 365)

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**How many significant figures does each of the following numbers have?**

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**Significant Figures** rules:

**Rule 1**: All non-zero digits are significant.

**Rule 2**: Zeros between other significant figures are significant.

**Rule 3**: Zeros to the right of a decimal point and to the right of a number are significant.

**Rule 4**: A zero standing alone to the left of a decimal point is not significant.

**Rule 5**: Zeros to the right of the decimal and to the left of a number are not significant.

**Rule 6**: Zeros to the right of the last number but left of the decimal point may or may not be significant. This information is known only to the person that made the measurement. Use scientific notation when in doubt. The use of a bar over the last significant zero is acceptable as well as using the decimal point to indicate that all digits to its left are significant.

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a) 6.21 -: **3 significant figures**

b) 62.1 –**:3 significant figures**

c) 0.620 –**:3 significant figures**

d) 6.2×10^{−2} **=: 2 significant figures**

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