Expert: Steve Holleran - 8/5/2008

Question
If the diameter of a circle is 1.3 x 10 to the -12 power meters, then what is its radius?

Answer
Hi Chase,

Well, if our diameter is 1.3 x 10^-12, then the radius is equal to this divided by 2:

              1.3 x 10^-12 / 2 = 1.3/2 x 10^-12 = 0.65 x 10^-12

But most answers will also be in Scientific notation, so you have to adjust this.  The first number in scientific notation must always be between 1 and 10, so we have to  make the 0.65 into 6.5.

This means instead of moving the decimal 12 places left to get our answer (when we had 0.65 x 10^-12), we've added an additional decimal place, so in sci. not., the answer has to look like

                   6.5 x 10^-13

I hope this helps out.
Steve