Max Maths, Year 5, Practice, Multiplying by 25 mentally

In a mathematics exercise designed for Year 5 students, the focus is on practicing the skill of mentally multiplying numbers by 25. The method presented simplifies the process by initially multiplying the given number by 100, which is a straightforward task as it involves simply adding two zeros to the end of the number. For example, when multiplying 18 by 25, students first calculate 18 × 100, which is an easier calculation and provides a larger number that is 100 times bigger than the original.

After obtaining the result of multiplying by 100, the next step is to divide this answer by 4. This division step is crucial as it effectively finds a quarter of the larger number, which is equivalent to the original task of multiplying by 25. For instance, with the number 18, after multiplying by 100, the students would divide their answer by 4 to arrive at the final result of 18 × 25. This technique is reinforced through practice problems, such as finding 14 × 25 using the same method. The exercise encourages students to view multiplying by 25 as a two-step process: making the number 100 times larger, then finding a quarter of it. To further practice and consolidate their skills, students are directed to workbook pages for additional exercises.