Maths Lesson Multiplication using the Associative Law Mental

Maths Lesson Multiplication using the Associative Law

Mental Starter Recite the • 8 times table • 9 times table • 10 times table

We are looking at a new way to multiply numbers. This video tells you about the associative law which sounds hard but it isn’t. You are going to see that it is REALLY EASY! It mentions parentheses – this word means curved brackets like this ( ) https: //www. youtube. com/watch? v=TGVGwr. M-vdo

Associative Law • Let’s practise the method step by step with the question below. • Write this question into your book. 2 x 4 x 5=

Now write it again putting the first 2 numbers in brackets. • (2 x 4)x 5= Work out the calculation in the brackets first. 8 x 5 = 40 The answer to 2 x 4 x 5 = 40

Now we will try it another way. • Can you think of how to write the question out using brackets? • Have a go before looking.

Rewrite the question and put the last 2 numbers in brackets 2 x (4 x 5) = 2 x 20 = 40 Remember – work out the part in brackets first. We got the same answer as last time. 2 x 4 x 5 = 40

• Well done! You have just used the Associative Law for multiplication. • You made the calculation easier by regrouping the numbers into brackets.

Associative Law

Use brackets to regroup the numbers and work out the answers. Tricky Trickier Trickiest

Answers 12 40 24 30 60 10

Answers 1. 330 2. 360 3. 108 4. 720 5. 360 6. 60 7. 480 8. 168 9. 126 10. 900

Answers 1. 5600 2. 4200 3. 648 4. 385 5. 1200 6. 189 7. 2000 8. 960 9. 960 10. 270

In depth Teach a grown up at home to use the Associative Law of multiplication. Grown ups too busy? Look in the mirror and talk it through to yourself! Either way, use the words regroup and brackets