Short multiplication
You learn to multiply a big number by one digit in columns, carrying as you go.
How to work it out
- Start on the right: multiply each digit.
- If 10 or more, write the ones and carry the tens to add to the next column.
43
×6
258
A worked example
43 × 6
- Ones: 6 × 3 = 18, write 8 and carry 1.
- Tens: 6 × 4 = 24, then add the 1 you carried: 24 + 1 = 25.
- The answer is 258.
More examples
124 × 6
- Ones: 6 × 4 = 24, write 4 and carry 2.
- Tens: 6 × 2 = 12, add the 2: 12 + 2 = 14, write 4 and carry 1.
- Hundreds: 6 × 1 = 6, add the 1: 6 + 1 = 7.
- The answer is 744.
124
×6
744
27 × 8
- Ones: 8 × 7 = 56, write 6 and carry 5.
- Tens: 8 × 2 = 16, then add the 5 you carried: 16 + 5 = 21.
- The answer is 216.
27
×8
216
Watch out
You add the carried digit before you multiply: for 43 × 6 you do 6 × 5.
First multiply the digit in the column, and only then add the digit you carried.
You forget the digit you carried: for 43 × 6 you write 248.
Write the carried digit small in the next column, so you can see it.
Tips
- Multiply the column first, then add the carried digit.
- Estimate first: 43 × 6 is about 40 × 6 = 240.
Exceptions
- If the last column makes more than 9, write the whole number down there.
Why it works
You multiply each digit of the big number by the single digit, from right to left. If the answer is more than 9, part of it belongs in the next column. You carry that part and add it in there.