Theme 3.  Addition and subtraction of numbers 8 and 9. Difference comparison of segment lengths

In the theme you learn:
• You will practice finding true equalities;
• You will learn how to add and subtract numbers 8 and 9 using a number line;
• You will learn to calculate expressions with addition and subtraction of numbers 8 and 9;
• You will practice solving problems to find the sum, the remainder, to increase a number by a few units, and to compare numbers by difference;
• You will find unknown parts and results of addition and subtraction actions;
• You will learn to compare named numbers shown in units of length – centimeters.