SME
Grade 3 Math · Operations & Algebraic Thinking
Use properties of multiplication
Use this for “Use 6 × 5 and 6 × 2 to find 6 × 7.”
Diagram
6 × 7 = 6 × 5 + 6 × 2 = 30 + 12
= 42
This is an example. Type your own values to start a new problem.
Rows
×
Columns
=
Rows
×
First part
+
Rows
×
Second part
=
Total
First product
worked out (not typed)
Second product
worked out (not typed)
Formulas
5 + 2 = 7
First part + second part = columns
6 × 5 = 30
Rows × first part = first product
6 × 2 = 12
Rows × second part = second product
30 + 12 = 42
First product + second product = total
6 × 7 = 42
Rows × columns = total
Assumptions
•
Break one factor into two parts you know: 7 = 5 + 2.
•
Multiply each part, then add: 6 × 7 = 6 × 5 + 6 × 2.
•
Parts of 5 or 10 are easiest.
Step-by-step
WE KNOW
Second part: 2
Rows: 6
First part: 5
FIND
columns, first product, second product, total
Step 1 · Find columns
5 + 2 = ?
First part + second part = columns
Add the first part and the second part.
Columns = 7
Step 2 · Find first product
6 × 5 = ?
Rows × first part = first product
Multiply the rows by the first part.
5 × 5 = 25
One more group: 25 + 5 = 30
First product = 30
Step 3 · Find second product
6 × 2 = ?
Rows × second part = second product
Multiply the rows by the second part.
5 × 2 = 10
One more group: 10 + 2 = 12
Second product = 12
Step 4 · Find total
30 + 12 = ?
First product + second product = total
Add the first product and the second product.
30 + 10 = 40
40 + 2 = 42
Total = 42
Check
Put the numbers back in. Both sides should match.
5 + 2 = 7 ✓
6 × 5 = 30 ✓
6 × 2 = 12 ✓
30 + 12 = 42 ✓
6 × 7 = 42 ✓
Topic check
See what you know: 5 questions on this topic
New questions each time. Pass to mark it complete.