Don't even know where to start..
volume of a sphere has decreased by 30 percent. how many percentage has the radius decreased?
When the radius of a sphere is multiplied by r,
the area is multiplied by r^2
the volume is multiplied by r^3.
So when the volume is multiplied by .7 = r^3,
r = ...
(Then subtract this from "1", as I did to get .7, and convert to a percentage if needed)
No its in my math book. I managed doing it the other way around, like ''the radius of a sphere grows by 12,5 percent, how many percentage will the volume increase?''.
Where i got ((1.125^3) -1)*100)=42%
I just don't get it when it decreases..