I'm struggling with this exercise at the moment;
Let F ⊂ Rn ⊂ Rm for some integers 0 ≤ n < m. Let s ≥ 0. Show that the s-dimensional Hausdorff measure of F is the same whether F is regarded either as a subset of $R^n$ or of $R^m$
I'm definitely missing something obvious but can't think where to begin. Can anyone help?