In Saxon Math Intermediate 4, Grade 4 students learn how to find missing numbers in subtraction equations using two strategies: "subtracting down" and "adding up." The lesson teaches students to apply the inverse relationship between addition and subtraction to solve for unknown values in problems where either the minuend or subtrahend is missing. Students practice checking their solutions by substituting the missing number back into the original equation.
Section 1
📘 Missing Numbers in Subtraction
Remember that we "subtract down" to find the bottom number and "add up" to find the top number.
Next, you'll use the 'add up' strategy to find missing numbers in subtraction problems and check your answers.
Section 2
Finding The Missing Piece
To find a missing number in a subtraction problem, remember that you can either “subtract down” to find the bottom number or “add up” to find the top number. Subtraction and addition are inverse operations, which means they undo each other.
Think of subtraction problems like a puzzle where you need to find the missing piece. You can either work backward from the start (subtract down) or build up from the answer (add up). The “add up” method is often a sneaky shortcut because our brains are awesome at adding!
Section 3
Subtract Down
When you know the starting number (the top number) and the result, you can find the number being subtracted by “subtracting down.” For example, to solve , you calculate .
This is the straightforward approach! It’s like knowing you had 14 cookies and now have 6 left. To find out how many you ate, you just subtract what’s left from what you started with. Simple as that! No tricks, just direct subtraction.
Section 4
Add Up
To find a missing number in subtraction, you can rephrase it as addition by adding the bottom two numbers. For example, is the same as asking .
This is the super-sleuth detective method! Flip the problem around and use your addition skills to crack the code. It’s often much easier to find what you started with by adding up the pieces you can see. It feels like a magic trick, but it's pure logic!
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Section 1
📘 Missing Numbers in Subtraction
Remember that we "subtract down" to find the bottom number and "add up" to find the top number.
Next, you'll use the 'add up' strategy to find missing numbers in subtraction problems and check your answers.
Section 2
Finding The Missing Piece
To find a missing number in a subtraction problem, remember that you can either “subtract down” to find the bottom number or “add up” to find the top number. Subtraction and addition are inverse operations, which means they undo each other.
Think of subtraction problems like a puzzle where you need to find the missing piece. You can either work backward from the start (subtract down) or build up from the answer (add up). The “add up” method is often a sneaky shortcut because our brains are awesome at adding!
Section 3
Subtract Down
When you know the starting number (the top number) and the result, you can find the number being subtracted by “subtracting down.” For example, to solve , you calculate .
This is the straightforward approach! It’s like knowing you had 14 cookies and now have 6 left. To find out how many you ate, you just subtract what’s left from what you started with. Simple as that! No tricks, just direct subtraction.
Section 4
Add Up
To find a missing number in subtraction, you can rephrase it as addition by adding the bottom two numbers. For example, is the same as asking .
This is the super-sleuth detective method! Flip the problem around and use your addition skills to crack the code. It’s often much easier to find what you started with by adding up the pieces you can see. It feels like a magic trick, but it's pure logic!
Book overview
Jump across lessons in the current chapter without opening the full course modal.
Continue this chapter