SME
Grade 3 Math · Problem type
Group factors to multiply
Use this to multiply three numbers, like 3 × 5 × 2, by picking an easy pair first.
Diagram
2 groups of 15
30 in all
First factor: 3
Second factor: 5
Last two multiplied: 10
This is an example. Type your own values to start a new problem.
First factor
×
Second factor
×
Third factor
=
First two multiplied
×
Third factor
=
First factor
×
Last two multiplied
=
Product
Formulas
3 × 5 = 15
First factor × second factor = first two multiplied
5 × 2 = 10
Second factor × third factor = last two multiplied
15 × 2 = 30
First two multiplied × third factor = product
3 × 10 = 30
First factor × last two multiplied = product
Assumptions
•
With three factors, multiply any two first. The product is the same.
•
So 3 × 5 × 2 = 15 × 2 = 3 × 10: pick the pair that makes an easy fact.
•
The picture draws each group as first × second dots.
Step-by-step
WE KNOW
First factor: 3
Second factor: 5
Third factor: 2
FIND
first two multiplied, last two multiplied, product
Step 1 · Find first two multiplied
3 × 5 = ?
First factor × second factor = first two multiplied
Multiply the first factor by the second factor.
Count by 5s, 3 times: 5, 10, 15 → 15
First two multiplied = 15
Step 2 · Find last two multiplied
5 × 2 = ?
Second factor × third factor = last two multiplied
Multiply the second factor by the third factor.
10 × 2 = 20. Five groups are half of that: 10
Last two multiplied = 10
Step 3 · Find product
15 × 2 = ?
First two multiplied × third factor = product
Pick the pair that makes an easy fact: multiply the first factor by the last two.
Easy pair: 3 × 10 = 30
The same product: 15 × 2 = 30
Product = 30
Check
Put the numbers back in. Both sides should match.
3 × 5 = 15 ✓
5 × 2 = 10 ✓
15 × 2 = 30 ✓
3 × 10 = 30 ✓
Topic check
See what you know: 5 questions on this topic
New questions each time. Pass to mark it complete.