homework help: given the diameter, what is the radius?

G

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Diameter of a cirlce:
If the diameter of a circle is 1.3 * 10(-12) meters, than what is it's radius?
The 10(-12) is the number 10 with a negative 12 exponent.
Thank you-Caron
 

jonboy

Full Member
Joined
Jun 8, 2006
Messages
547
Hello Caron!

If the diameter of a circle is 1.3 * 10(-12) meters, than what is it's radius?
The 10(-12) is the number 10 with a negative 12 exponent.
Thank you-Caron
Ok I am sure you know that the radius is half the diameter. Whenever using Scientic Notation you do not do \(\displaystyle \frac{10^-12}{2}=10^-6\) or anything funky like that.

So: \(\displaystyle \L \;\frac{1.3\,\bullet\,10^ -12}{2}=r\)


Divide 1.3 by 2: \(\displaystyle \;.65\,\bullet\,10^-12=r\)


In scientific notation we always want the decimal to be after the second-from-last number going from the left in this case.


Hence: \(\displaystyle \L \;6.5\,\bullet\,10^-13=r\)


Since making .65 -------> 6.5 that makes the decimal move closer, thus making us add another -1 to the exponent since it is now even further from the .65. Negative exponents means move the decimal to the left.


Hope this helps.
 

Denis

Senior Member
Joined
Feb 17, 2004
Messages
1,473
1.3 * 10^(-12)
= 1.3 / 10^12
= 13 / 10^13
Now dividing by 2:
= 6.5 / 10^13
= 65 / 10^14 : that's .000 000 000 000 65; quite a small circle :shock:
 
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