Max Maths, Year 5, Work Book, Multiplying by 19 or 21 mentally

The 'Max Maths Year 5 Workbook' offers an exercise aimed at enhancing students' ability to multiply by 19 or 21 mentally. The task requires pupils to solve a series of multiplication problems and then reflect on the mental strategies they employed to reach the answers. This methodical approach encourages students to develop and articulate their mental arithmetic techniques, fostering a deeper understanding of multiplication.

For instance, to multiply 19 by 6 (19 × 6), a student might first multiply 20 by 6 to get 120, and then subtract 6 to account for the extra 1 that was added to 19 to make it 20, resulting in a final answer of 114. Similarly, when multiplying 21 by 4 (21 × 4), the student could double 4 to get 8 and then double 21 to get 42, followed by multiplying 42 by 8 to arrive at the answer of 168. The exercise continues with more complex examples such as 19 × 12, 8 × 21, 15 × 19, and 19 × 7, each challenging students to utilise and improve their mental math skills. The workbook provides a structured approach to learning, ensuring that students not only practice arithmetic but also become more proficient in mental calculations.