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Balance subtraction equations

An equation is balanced when both expressions represent the same whole-number quantity, so a subtraction expression on one side may equal a number or another expression on the other side. Learners determine missing numbers in subtraction equations within 1,000 by using place-value reasoning, related addition facts, and the relationship between the minuend, subtrahend, and difference, rather than treating the equal sign as “the answer comes next.”

Detailed Explanation: Balance subtraction equations

An equation is balanced when both sides have the same value. The equal sign means “has the same value as,” not just “the answer comes next.”

Solve:

725−300=400+□725-300=400+\Box
  1. Find the value of the left side. Subtract 300300 from 725725:
725−300=425725-300=425

So the equation becomes:

425=400+□425=400+\Box
  1. Ask: “What number added to 400400 makes 425425?” Use a related addition fact or subtract:
425−400=25425-400=25
  1. Put 2525 in the box:
725−300=400+25725-300=400+25
  1. Check both sides:
725−300=425725-300=425

and

400+25=425400+25=425

Both sides equal 425425, so the equation is balanced. The missing number is 25\boxed{25}.

Learn by doing: Balance subtraction equations

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    Subtraction - Balance Equation - Two Digit, Three Terms

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