Mathematics
Grade 4
15 min
Solve for the variable: addition and subtraction
Solve for the variable: addition and subtraction
Tutorial Preview
1
Introduction & Learning Objectives
Learning Objectives
Define the terms 'variable' and 'equation' in their own words.
Identify the variable in a given addition or subtraction equation.
Use the inverse operation of subtraction to solve for a variable in an addition equation.
Use the inverse operation of addition to solve for a variable in a subtraction equation.
Check their solution by substituting the value of the variable back into the original equation.
Translate a simple one-step word problem into an equation with a variable.
You had 12 pencils, but now you only have 7. How many did you lose? ✏️ We can use a secret code with letters to find the missing number!
In this lesson, you'll become a math detective! We'll learn how to find the value of a missing number, called a varia...
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Key Concepts & Vocabulary
TermDefinitionExample
VariableA letter or symbol that takes the place of an unknown number in an equation.In the equation `x + 8 = 14`, the letter `x` is the variable.
EquationA mathematical sentence that shows two expressions are equal. It always has an equals sign (=).`15 - 5 = 10` is an equation. `y + 7 = 20` is also an equation.
Inverse OperationsOperations that are opposites and 'undo' each other. Addition and subtraction are inverse operations.If you add 5 to a number, you can undo it by subtracting 5.
SolutionThe value of the variable that makes the equation true.In `n + 3 = 10`, the solution is `n = 7` because `7 + 3 = 10`.
Balance the EquationAn equation is like a balanced scale. To keep it balanced, whatever you do to one side of the equals sign, you must also do to th...
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Core Formulas
Subtraction Property of Equality
If `a + b = c`, then `a = c - b`
To solve an addition equation and find the variable, you use the inverse operation: subtraction. Subtract the same number from both sides of the equation to isolate the variable.
Addition Property of Equality
If `a - b = c`, then `a = c + b`
To solve a subtraction equation and find the variable, you use the inverse operation: addition. Add the same number to both sides of the equation to isolate the variable.
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Challenging
According to the Addition Property of Equality, if `m - p = q`, which statement must also be true?
A.m = q - p
B.p = m + q
C.m = q + p
D.q = m + p
Challenging
Consider two equations. Equation 1: `p + 20 = 60`. Equation 2: `q - 20 = 60`. How does the value of `p` compare to the value of `q`?
A.The value of p is greater than the value of q.
B.The value of p is less than the value of q.
C.The value of p is equal to the value of q.
D.It is impossible to compare p and q.
Challenging
A video game has `g` levels in total. After you complete 19 levels, there are 32 levels left to win. A friend claims the game has 50 levels in total. Is your friend correct?
A.Yes, because 32 + 19 = 51, which is close to 50.
B.No, because the correct equation is g + 19 = 32, and g = 13.
C.Yes, because the correct equation is 32 - 19 = g, and g = 13.
D.No, because the correct equation is g - 19 = 32, and g = 51.
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