The strategy
How it works
Split one factor into tens and ones.
Multiply the other factor by each part.
Add the partial products and do a quick estimate.
See it in action
Worked examples
Example 124 × 13
- Split 13 into 10 + 3.
- 24 × 10 = 240; 24 × 3 = 72.
- 240 + 72 = 312.
Answer: 312
Example 232 × 12
- Split 12 into 10 + 2.
- 32 × 10 = 320; 32 × 2 = 64.
- 320 + 64 = 384.
Answer: 384
A quick heads-up
Common mistakes to avoid
- Dropping a zero in the tens product; 24 × 10 is 240, not 24.
- Adding the partial products before calculating them; keep each line separate.
Your turn
Check your understanding
Choose an answer to see instant feedback and a short explanation. You can take the quiz again any time.
Question 1 of 3
What is 15 × 12?
15 × 10 = 150 and 15 × 2 = 30; 150 + 30 = 180.
What is 21 × 14?
21 × 10 = 210 and 21 × 4 = 84; total 294.
What is 30 × 16?
3 × 16 = 48, then multiply by ten: 480.
Keep the momentum
Try a few practice problems
Choose a comfortable range and work through a short round with the free mental math trainer.