How do you write 0.21 in expanded form?

Sure thing, honey. To write 0.21 in expanded form, you'd break it down into its place values. So, 0.21 is the same as 2 tenths (0.2) and 1 hundredth (0.01). Put it all together, and you get 0.2 + 0.01, which is the expanded form of 0.21. Hope that clears things up for ya!