Mathematics
Grade 3
15 min
Subtraction input/output tables - up to three digits
Subtraction input/output tables - up to three digits
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1
Introduction & Learning Objectives
Learning Objectives
Identify the subtraction rule in an input/output table by comparing an input and its corresponding output.
Complete a subtraction input/output table by applying a given rule to find missing outputs.
Determine a missing input when the output and the subtraction rule are known.
Write the rule for a given subtraction input/output table in the format 'Input - X = Output'.
Solve one-step word problems that can be represented by a subtraction input/output table.
Accurately subtract three-digit numbers with and without regrouping to solve for outputs.
Imagine a secret code machine! 🤖 If you put the number 250 in and the number 225 comes out, can you figure out the machine's secret subtraction rule?
In this lesson, we will explore input/output ta...
2
Key Concepts & Vocabulary
TermDefinitionExample
Input/Output TableA table with two columns that shows how one number (the input) is changed by a rule to become another number (the output).A table with an 'Input' column showing 100, 200, 300 and an 'Output' column showing 90, 190, 290.
InputThe number you start with in an input/output table. It's the number that goes 'in' to the rule.If the rule is 'Subtract 50', and you start with 150, then 150 is the input.
OutputThe number you get after the rule has been applied to the input. It's the number that comes 'out'.If the input is 150 and the rule is 'Subtract 50', the output is 100.
RuleThe mathematical operation that consistently changes every input into its matching output.In a table where input 7...
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Core Formulas
Finding the Output
Input - Rule Number = Output
Use this formula when you know the starting number (Input) and the rule. Subtract the rule number from the input to find the result (Output).
Finding the Rule
Input - Output = Rule Number
Use this formula when you have a complete pair of Input and Output numbers. Subtract the output from the input to discover the secret rule number.
Finding the Input
Output + Rule Number = Input
Use this formula when you need to find the starting number. This uses the inverse (opposite) operation. Add the rule number to the output to work backward and find the input.
4 more steps in this tutorial
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Challenging
The rule for a table is 'Subtract 125'. If the output is 789, what was the input?
A.664
B.914
C.814
D.674
Challenging
In Table 1, the rule is 'Subtract 40'. In Table 2, the rule is 'Subtract 60'. The output from Table 1 becomes the input for Table 2. If the starting input for Table 1 is 500, what is the final output from Table 2?
A.400
B.460
C.440
D.300
Challenging
The rule for an input/output table is to subtract the number of minutes in two hours. What is the output for an input of 875?
A.873
B.815
C.755
D.655
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