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Write each measurement in meters using scientific notation in the form \(a\times10^k\), where \(1\le a<10\).
a) A paramecium is \(0.25\,\text{mm}\) long.
b) A typical bacterium has a diameter of \(2\,\mu\text{m}\).
c) A virus is \(25\,\text{nm}\) across.
Hints
- Express each metric prefix as a power of \(10\).
- Move the decimal point until the coefficient is at least \(1\) and less than \(10\).
- Adjust the exponent to compensate for the decimal shift.
Solution
1. Since \(1\,\text{mm}=10^{-3}\,\text{m}\), \(0.25\,\text{mm}=0.25\times10^{-3}\,\text{m}=2.5\times10^{-4}\,\text{m}\).
2. Since \(1\,\mu\text{m}=10^{-6}\,\text{m}\), \(2\,\mu\text{m}=2\times10^{-6}\,\text{m}\).
3. Since \(1\,\text{nm}=10^{-9}\,\text{m}\), \(25\,\text{nm}=25\times10^{-9}\,\text{m}=2.5\times10^{-8}\,\text{m}\).
Answer
a) \(2.5\times10^{-4}\,\text{m}\)
b) \(2\times10^{-6}\,\text{m}\)
c) \(2.5\times10^{-8}\,\text{m}\)
