Balance subtraction equations - up to three digits

Learning Objectives Define a balanced equation and identify the variable. Use inverse operations (addition) to find an unknown value in a subtraction equation. Solve for a variable when it is the minuend (the starting number). Solve for a variable when it is the subtrahend (the number being subtracted). Balance subtraction equations with numbers up to three digits. Verify a solution by substituting the value back into the original equation. Imagine a seesaw with numbers on each side. How can we make it perfectly level, even if one number is a mystery? 🤔 In this lesson, you'll become an equation detective! You will learn how to find a missing number, called a variable, in a subtraction problem to make both sides of the equals sign perfectly balanced. This skill is like...

TermDefinitionExample EquationA math sentence that says two things are equal, using an equals sign (=).The sentence `150 - 50 = 100` is an equation. VariableA letter or symbol that stands for an unknown number.In the equation `200 - x = 150`, the letter `x` is the variable. Balanced EquationAn equation where the value on the left side of the equals sign is the same as the value on the right side.In `300 - 100 = 200`, both sides have a value of 200, so it is balanced. Inverse OperationsOperations that 'undo' each other. Addition is the inverse of subtraction.To undo subtracting 25 from a number, you would add 25 back to it. MinuendThe number you are subtracting from; the starting amount.In `125 - 25 = 100`, the minuend is 125. SubtrahendThe number that is being subtracted or take...

The Missing Minuend Rule If `x - a = b`, then `x = a + b` When the number you are subtracting *from* is missing, you must add the other two numbers together to find it. Use the inverse operation! The Missing Subtrahend Rule If `a - x = b`, then `x = a - b` When the number being *subtracted* is missing, you must subtract the difference from the starting number (the minuend) to find it.