Addition and subtraction within 20 - Subtraction crossing 10 - Worksheet

In Lesson 11 of the 'Fluency & Precision' series, young learners are introduced to the concept of subtraction crossing 10. The National Curriculum objective for this lesson is to enable students to read, write, and interpret mathematical statements involving addition (+), subtraction (–), and equals (=) signs, and to add and subtract one-digit and two-digit numbers to 20, including zero. To facilitate this learning, practical equipment like Base 10 is recommended, which helps children visually differentiate between hundreds, tens, and ones. The lesson is supported by differentiated worksheets and teaching slides, and key vocabulary includes terms such as 'subtraction', 'ten', and 'number lines'. This step focuses on the strategy of partitioning to make ten, using ten frames and number lines to model the structure of this strategy, with the aim of children developing this into a mental strategy.

The worksheet provides examples where numbers are already partitioned to guide children in understanding how to cross 10 on a number line. It progresses from examples to follow, to incomplete questions that require the children to use clues to complete the subtraction and write the number sentence. The 'Reasoning & Problem Solving' section challenges students to identify errors in given calculations and to compare subtraction statements using less than (<), greater than (>), or equals (=) signs. The activities are designed to encourage critical thinking and to help students understand the relationship between subtraction and partitioning, leading them to greater mastery of the concept of crossing 10 in subtraction within the range of 20.