Mathematics
Grade 3
15 min
Divide by 9
Divide by 9
Tutorial Preview
1
Introduction & Learning Objectives
Learning Objectives
Recall multiplication facts for 9 to solve division problems.
Identify the relationship between multiplying by 9 and dividing by 9 using fact families.
Solve one-step word problems that require dividing by 9.
Represent division by 9 using models like equal groups or arrays.
Use the 'sum of digits' trick to check if a two-digit number is divisible by 9.
Accurately find the quotient for any division fact with 9 as the divisor, up to 81 ÷ 9.
If you have 36 toy cars and 9 boxes, how many cars can you put in each box to be fair? 🏎️ Let's learn a super skill to find out!
In this lesson, we will become experts at dividing by 9. You will learn how division is the opposite of multiplication and discover some cool tricks that make dividing by 9 easy...
2
Key Concepts & Vocabulary
TermDefinitionExample
DivisionThe action of splitting a number into equal parts or groups.27 ÷ 9 means splitting 27 into 9 equal groups.
DividendThe total number that you are dividing up.In the problem 54 ÷ 9 = 6, the dividend is 54.
DivisorThe number you are dividing by. It tells you how many groups to make.In the problem 54 ÷ 9 = 6, the divisor is 9.
QuotientThe answer to a division problem. It tells you how many are in each group.In the problem 54 ÷ 9 = 6, the quotient is 6.
Fact FamilyA set of four related multiplication and division facts that use the same three numbers.The fact family for 5, 9, and 45 is: 5 × 9 = 45, 9 × 5 = 45, 45 ÷ 9 = 5, 45 ÷ 5 = 9.
Equal GroupsGroups that all have the same number of items.18 ÷ 9 can be shown as 9 equal groups with 2 items in each group.
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Core Formulas
Inverse Operation Rule
a \div 9 = b \quad \text{is the same as} \quad b \times 9 = a
Use this rule to turn a division problem into a multiplication problem. If you know your 9s times tables, you can easily find the answer to a division problem.
The 'Sum of Digits' Divisibility Trick
\text{For a two-digit number 'ab', if } a + b \text{ is a multiple of 9, the number is divisible by 9.}
This is a quick way to check if a number can be divided by 9 evenly. For example, for the number 63, add the digits: 6 + 3 = 9. Since 9 is divisible by 9, 63 is too.
The 'Tens Digit + 1' Pattern
\text{For a two-digit dividend 'ab', the quotient is } a + 1.
This is a special shortcut for dividing by 9 (for dividends from 18 to 81). Look at the tens...
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Challenging
Which story problem can be solved with the equation 36 ÷ 9 = 4?
A.girl has 36 dolls and gets 9 more. How many does she have now?
B.boy has 9 toy cars and 4 toy trucks. How many toys does he have?
C.baker bakes 36 muffins and places them equally into 9 boxes. How many muffins are in each box?
D.teacher has 36 students, and 4 of them are absent. How many students are present?
Challenging
Mia solved 54 ÷ 9 = 5. Her teacher said she made a common 'off by one' mistake. What is the correct thinking process?
A.She should have subtracted 9 from 54.
B.She was close; she needed to remember that 6 × 9 = 54, not 5 × 9.
C.She mixed up the dividend and the divisor.
D.She should have used the 'sum of digits' trick, which is 5+4=9.
Challenging
The answer (quotient) to a division problem is 7. The number we divided by (divisor) is 9. What was the starting number (dividend)?
A.63
B.16
C.2
D.79
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