How many circles (radius – r) are needed to cover circle which radius is 2 times bigger (radius – 2r).

I think we need to use area which is $S=\pi R^2$ but I don't really know what to do

How many circles (radius $r$) are needed to cover circle whose radius is $2$ times bigger (radius $2r$).

I think we need to use area which is $S=\pi R^2$ but I don't really know what to do.