a cylinder is basically lots of circles stacked on top of each other so equation for volume of cylinder is (area of circle formula) times height
area of circle formula=pi times r^2
so volume of cylinder=pi times r^2 times height
volume=980 in
volume=pi times r^2 times height
height =20
subsitute
980=pi times r^2 times 20
divide both sides by 20
49=pi times r^2
divide both sides by pi
[tex] \frac{49}{pi} [/tex]=r^2
square root both sides (remember that [tex] \sqrt{ \frac{x}{y} }= \frac{ \sqrt{x} }{ \sqrt{y} } [/tex]) so
[tex] \frac{49}{pi} [/tex]=[tex] \frac{ \sqrt{49} }{ \sqrt{pi}} = \frac{7}{ \sqrt{pi} } [/tex]=r
try to make there be no radical (√) in the bottom so multiply top and bottom by [tex] \frac{ \sqrt{pi} }{ \sqrt{pi} } [/tex]
[tex] \frac{7}{ \sqrt{pi} } [/tex] times [tex] \frac{ \sqrt{pi} }{ \sqrt{pi} } [/tex]=[tex] \frac{7 \sqrt{pi} }{pi} [/tex]=radius≈(if aprox pi to 3.14)3.94933 in
the answer is (7√pi)/pi in or aprox 3.95 in
