3000 examples in mathematics. Best training. Fold. We subtract. Examples with "windows". 4th grade

The manual contains examples on the basic topic of mathematics course for grade 4 Addition and subtraction in the range of 1000.
In the examples with “windows”, one of the components of addition (first or second term) and subtraction (reduced or subtracted) or a sign of action were missed. The child must determine what is missed in the example and how to find it. Such examples are excellent training for the formation of the skill of performing oral calculations, as well as for the development of the ability to establish causal relationships when choosing a solution method.
Methodological recommendations on the second and third sides of the cover will help effectively organize work in the class and houses