# What is the total area available for data storage in square cm if the data is stored between a radius of 2.3 cm and 5.7 cm?

Jan 24, 2015

$85.4 c {m}^{2}$

I suppose you have a situation like this:

where you are interested in the area between the two circles (in green).
This area can be the difference between the one of the big circle and the one of the small circle (where, area of the circle is $A = \pi {r}^{2}$), or:

$A = {A}_{{r}_{2}} - {A}_{{r}_{1}}$

$A = \pi {\left({r}_{2}\right)}^{2} - \pi {\left({r}_{1}\right)}^{2} =$

$= \pi \left({5.7}^{2} - {2.3}^{2}\right) = 85.4 c {m}^{2}$