Some children have difficulty realising that the same numbers can be written in different ways, especially when dealing with decimals and decimal fractions. This page is a good test of understanding, probably most suited for year 5 children (/10 yrs old).
0.23 can be read as 23 hundredths or 2 tenths and 3 hundredths. As a fraction it would be written as 23/100.
With a number such as four and three hundredths it is important to keep the zero in the tenths so that it is written as 4.03.
Watch out for a common mistake on a question such as thirteen hundredths when children write 0.013; the one digit has been placed in the hundredths column when it should be in the tenths with the 3 digit in the hundredths.