A symbol such as a box, question mark, or letter can represent an unknown whole number in an equation, whose value is determined by the relationship that makes the equation true, whether it appears before, between, or after known numbers (for example, □ + 7 = 12 or 15 − □ = 9). This understanding applies to addition and subtraction with whole numbers within 100 and supports reasoning about equality and inverse operations, not generalized variables, negative numbers, or formal algebraic manipulation.
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Detailed Explanation: Use a symbol for an unknown
A symbol can stand for a number we do not know yet. We find its value by making the equation true.
Example:
- Read the equation: “15 minus a number equals 9.”
- Think: What number can we take away from 15 to leave 9?
- Count up from 9 to 15:
So, the missing number is .
Check the answer:
The equation is true, so is the value of .
Learn by doing: Use a symbol for an unknown
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Practice:
Linear Equation - Solve for Box, Two Terms, Add and Subtract
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Download/Modify Free Grade 2 'Use a symbol for an unknown' Worksheet
Print this free 'Use a symbol for an unknown' worksheet to practice this skill away from the computer. Click 'Modify' to easily customize this worksheet to your exact needs.
This Worksheet Includes:
- Linear Equation - Solve for Box, Two Terms, Add and Subtract
- Addition - Missing Value, 2 Digit, 1 Number
- Subtraction - Missing Value, From Multiples of Tens
- Addition & Subtraction - Balance Equation - Two Digit, Two Terms
- Addition & Subtraction - Balance Equation - Two Digit, Three Terms
- Addition - Missing Value, Within 5
- Subtraction - Balance Equation - One Digit, Two Terms
- Subtraction - Missing Value, Within 5
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