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

[Guest]

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]

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]

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: