Quick answer
Mental multiplication becomes manageable when you break a large problem into smaller ones using place value and the distributive property.
Split a number into tens and ones
For 23 × 14, calculate 23 × (10 + 4) = 230 + 92 = 322.
Multiply by 25 using quarters
Because 25 = 100/4, 48 × 25 = 4800/4 = 1200.
Use nearby round numbers
For 19 × 21, think (20 - 1)(20 + 1) = 20² - 1 = 399.
Worked examples
23 × 14 = 32248 × 25 = 120019 × 21 = 399
Common mistake to avoid
Do not forget to add every partial product. In 23 × 14, 23 × 4 is 92, not 82.
Practice questions
Try these without looking at the answers first. Explain your reasoning aloud or write each step.
- Question:
12 × 15— Answer:180 - Question:
36 × 25— Answer:900 - Question:
29 × 31— Answer:899
What to learn next
Review the related lessons linked below, then practice independently. If you make an error, write down which rule you used and why it did not apply.