Max Maths, Year 5, Learn together, Multiplying by 25 mentally (1)

Max Maths Year 5 introduces a mental strategy for multiplying by 25 that simplifies the process and makes it more approachable for students. The method involves two main steps: multiplying the given number by 100 and then dividing the result by 4. This technique takes advantage of the fact that 25 is a quarter of 100, so by scaling up and then scaling down appropriately, the multiplication by 25 is achieved. For example, to multiply 16 by 25, students first calculate 16 multiplied by 100 to get 1,600. Then, to find one quarter of this result, they halve 1,600 to get 800, and halve again to reach 400. Thus, 25 times 16 equals 400.

Another example provided in the curriculum is multiplying 6 by 25. Students are encouraged to first multiply 6 by 100, resulting in 600. Since 100 is four times greater than 25, the next step is to divide 600 by 4, which equals 150. This demonstrates that 6 times 25 is 150. By breaking down the multiplication into these simpler steps of multiplying by 100 and finding a quarter of the result, students can quickly and efficiently calculate products involving the number 25 without relying on a calculator or long multiplication.