Grade 3 · Algebra & Patterning
One-Step Equations with an Unknown Number
One-step equations in Grade 3 formalize the change-in-quantity thinking from Grades 1 and 2. n + 15 = 20 asks: what number, when 15 is added, gives 20? Students who have experience with build-and-change tasks and unknown-addend problems already know how to reason about this. The symbolic equation is the formal notation for that reasoning. Verifying by substitution is a habit of mind that transfers to all of algebra: the answer must make the equation true.
LESSON VIDEO
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Lesson video
A short walkthrough to play in class or assign for flipped/at-home viewing.
WHAT STUDENTS WILL LEARN
✓Solve one-step addition and subtraction equations with an unknown in all positions: start, change, or result unknown
✓Record unknowns symbolically using a box or the letter n
✓Verify solutions by substituting back into the equation
✓Connect equation structures to even and odd number investigations
✓Apply equations to real-world problem situations