Multiply by 9

Learning Objectives Recall all multiplication facts for 9, from 9 x 1 to 9 x 10, with speed and accuracy. Demonstrate the 'Tens Minus One' strategy to solve any multiplication problem with 9. Use the 'Finger Trick' as a physical tool to find the product of a number and 9. Identify and describe the two main patterns in the 9s multiplication table (the 'Sum of Digits' and 'Tens Digit' patterns). Solve one-step word problems that require multiplying by 9. Check their answers to a 9s multiplication problem using a different strategy, such as repeated addition. Did you know the number 9 has a secret code hidden in its multiplication facts? 🤫 Let's become math detectives and uncover its secrets! In this lesson, we will focus only on m...

TermDefinitionExample MultiplicationA fast way of doing repeated addition. It's when you take one number and add it together a certain number of times.9 x 4 is the same as 9 + 9 + 9 + 9, which equals 36. FactorThe numbers that are being multiplied together in a multiplication problem.In the problem 9 x 5 = 45, the numbers 9 and 5 are the factors. ProductThe answer you get when you multiply two or more factors together.In the problem 9 x 5 = 45, the number 45 is the product. PatternSomething that repeats in a way we can predict. Math patterns help us solve problems more easily.The products of the 9s facts (9, 18, 27, 36...) have a pattern where the digits always add up to 9. Commutative PropertyThis property says you can swap the order of the factors and you will still get the same pr...

The 'Tens Minus One' Trick 9 \times n = (10 \times n) - n To multiply any number (n) by 9, first multiply it by 10 (which is easy, just add a zero!), and then subtract the original number (n) from the result. The 'Sum of Digits' Pattern For 9 \times n (where n is 1-10), the digits of the product add up to 9. This is a great way to check your answer. For example, if you solve 9 x 8 and get 72, you can check it by adding the digits: 7 + 2 = 9. If they don't add up to 9, you made a mistake. The 'Tens Digit' Pattern For 9 \times n (where n is 1-10), the tens digit of the product is n - 1. The digit in the tens place of your answer will always be one less than the number you are multiplying by 9. For 9 x 5, the tens digit will be 4 (beca...