The ‘tee’ sound at the end of 20, 30 and so on, can be very difficult to distinguish from the ‘teen’ sound. The difference when hearing and saying ‘teen’ and ‘ty’ numbers needs to be reinforced and linked to how they are written and read. If pupils are already secure with ‘teen’ numbers, this is much easier.
A useful audio and visual clue is to link the ‘tee’ sound and the zero at the end of the ‘ty’ numbers to a ‘cup of tea’. When saying 70, we hear ‘seven-tea’ and can write turning the zero into ‘a nice hot cup of tea’.