A focused Grade 3 learning session for Unknown Number in Equations using visual models, worked examples, strategy guidance, and a short mastery check.
Student goal: I can find the missing number in a multiplication or division equation.
Unknown Number in Equations means using place value, operations, and equations to reason accurately with numbers.
Question: Look at the fact family: Which equation is part of this fact family?
| \(3\times8=24\) | \(8\times3=24\) |
|---|---|
| \(24\div3=8\) | \(24\div8=3\) |
Why it works: In this fact family, \(24\div3=8\). This is the division equation that matches the multiplication \(3\times8=24\).
Answer: \(24\div 3 = 8\)
Question: A balance scale shows 3 equal weights on one side and 15 on the other. Each weight is the same. What is the unknown weight? \(\)\square\times3=15\(\)
Answer: \(5\)
Question: Look at this array. It has 3 rows and \(\square\) columns. There are 21 dots in total. \(\)3\times\square=21\(\)
Answer: \(7\)
Question: Ava has 6 bags of marbles. Each bag has the same number of marbles. She has 42 marbles in all. How many marbles are in each bag? \(\)6\times\square=42\(\)
Why it works: Divide: \(42\div6=7\) marbles per bag. Check: \(6\times7=42\).
Answer: \(7\)
Unknown Number in Equations becomes easier when students connect the question to a model, use clear steps, and explain why the answer fits.
Understand the model before choosing the operation.
Use scratch paper. The explanation matters more than simply seeing whether the choice is correct.
What number makes the equation true? \(\)\square\times7=42\(\)
Answer D: \(6\)
Think: \(42\div7=6\), so the unknown is \(6\). Check: \(6\times7=42\).
What number makes the equation true? \(\)\square\times5=35\(\)
Answer D: \(7\)
Use the inverse: \(35\div5=7\). Check: \(7\times5=35\).
What number makes the equation true? \(\)9\times\square=54\(\)
Answer D: \(6\)
Divide: \(54\div9=6\). Check: \(9\times6=54\).
What number makes the equation true? \(\)8\times\square=32\(\)
Answer A: \(4\)
Think: \(32\div8=4\). Check: \(8\times4=32\).
What number makes the equation true? \(\)\square\times6=48\(\)
Answer D: \(8\)
Divide: \(48\div6=8\). Check: \(8\times6=48\).
What number makes the equation true? \(\)20\div4=\square\(\)
Answer D: \(5\)
Think: \(5\times4=20\), so \(20\div4=5\).
What number makes the equation true? \(\)24\div3=\square\(\)
Answer D: \(8\)
Use the inverse: \(8\times3=24\), so \(24\div3=8\).
What number makes the equation true? \(\)30\div5=\square\(\)
Answer D: \(6\)
Think: \(6\times5=30\), so \(30\div5=6\).
What number makes the equation true? \(\)\square\div4=6\(\)
Answer D: \(24\)
Use the inverse: \(6\times4=24\), so \(24\div4=6\). Check: \(24\div 4=6\).
What number makes the equation true? \(\)\square\div3=7\(\)
Answer D: \(21\)
Multiply: \(7\times3=21\). Check: \(21\div3=7\).
What number makes the equation true? \(\)\square\div5=8\(\)
Answer D: \(40\)
Use the inverse: \(8\times5=40\), so \(40\div5=8\).
