Posted by Peter on 24th August 2009

Mental Arithmetic: Subtracting 19 from 2-digit numbers

This is very similar to the process of adding 19 to a 2-digit number. The easiest way to do this is usually to take twenty and then add one. This mental arithmetic method is much quicker than carrying out the question using pencil and paper methods.If children can grasp these ideas it gives them a great deal of confidence and they can develop their own mental methods of answering other, similar questions; eg subtract 18 by taking 20 and then adding 2, or subtracting 39 by taking forty and adding one.