We investigate the problem of approximating function f in the power-type
weighted variable exponent Sobolev space Wr,p(.) ?(.) (0,1), (r = 1, 2,
...), by the Hardy averaging operator A (f) (x) = 1/x ?x0 f(t)dt. If
the function f lies in the power-type weighted variable exponent Sobolev
space Wr,p(.) ?(.)(0, 1), it is shown that A||(f)?f|| p(.),?(.)?rp(.) ?
C ||f(r) p(.),?(.) , where C is a positive constant. Moreover, we consider
the problem of boundedness of Hardy averaging operator A in power-type
weighted variable exponent grand Lebesgue spaces Lp(.),? ?(.)(0,1). The
sufficient criterion established on the power-type weight function ?(.) and
exponent p(.) for the Hardy averaging operator to be bounded in these
spaces.