Discovering how multiplication and division work together as opposite operations.
If you know that , you already know the answer to without even trying! How can one math problem secretly give you the answer to another?
Multiplication and division are like a pair of shoes—they belong together! In math, we call them inverse operations. This means they do the exact opposite of each other. Multiplication takes small, equal groups and puts them together to find a big total. Division takes that big total and breaks it back down into small, equal groups. If multiplication 'builds' a tower of blocks, division 'takes it apart' block by block. Because they are opposites, if you know one multiplication fact, you can use it to solve two different division problems!
Quick Check
If multiplication 'builds' a total, what does division do?
Answer
Division breaks a total apart into equal groups.
A fact family is a group of math facts that all use the same three numbers. Just like people in a family are related, these numbers are stuck together! For any three numbers like , , and , you can make four different facts: two multiplication and two division.
1. 2. 3. 4.
Notice how the biggest number () is always the answer in multiplication, but it is always the starting number in division!
Let's use the numbers , , and . 1. Start with multiplication: . 2. Flip the factors: . 3. Start with the total for division: . 4. Use the other factor: .
Quick Check
In the fact family for , what is ?
Answer
2
Sometimes, a math problem has a 'hole' in it, like . Because multiplication and division are linked, you can use a related fact to find the answer. To solve , you can ask yourself: 'How many groups of fit into ?' This is the same as solving . By using the operation you know best, you can solve the one that looks tricky!
Solve for the missing number: . 1. Think: 'What number divided into groups gives me in each group?' 2. Use the inverse: Change the division into multiplication. 3. Calculate: . 4. The missing number is !
A toy store has wheels. Each toy car needs wheels. How many cars can they build? 1. Write the equation: 2. Use a related multiplication fact: 3. Count by s: . That is steps. 4. Answer: They can build cars.
Which equation belongs in the same fact family as ?
Solve for the missing number:
In a fact family, the multiplication equations and division equations use different numbers.
Review Tomorrow
Tomorrow, try to explain to a friend or family member what an 'inverse operation' is and give one example.
Practice Activity
Look around your house for groups of items (like a carton of 12 eggs). Try to write the full fact family for that number! (Example: , , , ).