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.