How to create interrelated sliders?

Question

Say I want a slider that controls the value of $x$ and another slider that controls the value of $2x$, how would I go about it?

Answer 1

This?

{Slider[Dynamic[x], {0, 10}], 
 Slider[Dynamic[2 x, Set[x, #/2] &], {0, 20}]}

The documentation explains, under More Information, that "Dynamic[expr,f] makes interactive operations not change expr except by virtue of the evaluation of f[val,expr]. ". Otherwise, Mathematica attempts to assign a value to 2x.