A good way of working with decimals is to use shapes which are divided into ten equal parts. The shape is one whole unit and each part is one tenth, which can be written as 0.1.
This page has a selection of shapes and asks the child to write down the amount that has been shaded. Where all parts of a shape have been shaded this counts as ten tenths, or one whole one.
Whilst printed pages nearly always show the decimal point situated on the line most schools show it as half way up the line: the most important thing is that it shows up clearly.
This page can be found in our Year 4 maths worksheets in the Counting and Number category.