Efficient multiplication is a method of multiplying numbers quickly and accurately, without having to repeatedly add one number to itself. There are several techniques for efficient multiplication that can be taught in Year 4 math, including:
- Multiplication by 10, 100, and 1000: To multiply a number by 10, 100, or 1000, simply add one, two, or three zeroes to the end of the number.
For example, to multiply 8 by 10, we add a zero to the end of 8, making it 80. To multiply 8 by 100, we add two zeroes to the end of 8, making it 800.
Using a multiplication table: A multiplication table is a chart that shows the product of two numbers. Children can memorize the products of certain numbers, such as 2 x 4 = 8, and use them to quickly find the product of other numbers that are close to them, such as 7 x 4.
Using the distributive property: The distributive property states that a(b + c) = ab + ac. This can be used to break down a multiplication problem into smaller parts that are easier to solve.
For example, to multiply 8 x 7, we can use the distributive property and say 8 x (5 + 2) = 8 x 5 + 8 x 2 = 40 + 16 = 56.
- Mental Math: To perform mental math, children can use their knowledge of number facts and place value to solve problems quickly and accurately. For example, if a child knows that 3 x 7 = 21, they can quickly find the product of 30 x 7 by adding a zero to the end of 21 and getting 210.
It is important to note that these techniques are not mutually exclusive and they can often be combined to solve more complex problems.