Multiplication and Division - Efficient Multiplication - Presentation

Today's lesson focuses on enhancing students' multiplication skills by teaching them various efficient methods to solve complex multiplication problems mentally. The concept of efficiency in calculation is introduced, prompting students to consider what it means to multiply numbers in a way that saves time and effort. One example explored is calculating 25 x 8 using different strategies. The first method breaks the problem down into simpler parts by separating 25 into 20 and 5, then multiplying each by 8, and finally adding the results together. This method utilises the fact that if a student can multiply 2 x 8, they can easily scale up to 20 x 8.

Another method presented involves multiplying 25 by 8 through recognising it as 5 x 5 x 8 and visualising this as five instances of 5 x 8. A third strategy transforms the problem into 25 x 10 minus 2 x 25, simplifying the multiplication by working with a base of 10 and then adjusting by subtracting the excess. The fourth method doubles 25 to 50 and then halves the result after multiplying by 8, balancing the equation to find the correct answer. Students are encouraged to think critically about these methods and discuss which they find most efficient. The lesson also delves into reasoning activities, where students correct mistakes in multiplication and explore different multiplication strategies, further solidifying their understanding of efficient multiplication techniques.