
Operations with natural numbers I 

In this unit, basic concepts of natural numbers are revised and the operations of addition and subtraction are practised. Numbers that appear in each window are generated at random. This allows you to use the window indefinitely and practise a lot of different exercises. Numbers consist of only one or two figures so the calculations can easily be done mentally. Magic squares are used in the exercises, however the main objective of this unit is to learn things about natural numbers. 


Eduardo Barbero Corral 
Spanish Ministry of Education. Year 2007  
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