Multiplying large numbers - traditional method

If this method seems familiar it might be because you were encouraged to use it in school. Talking through the method is far easier than trying to follow written instructions. Have a look at the examples.

Have a look at how the sum 235 x 5 can be worked out using this method.

Step 1: 5 x 5 = 25. Put the 5 in the units column, and carry the 2 to the tens.
Step 2: 3 x 5 = 15. Add the 2 makes 17.
7 goes into the tens column and carry the 1 to the hundreds column.
Step 3: 5 x 2 = 10. Add the carried 1 makes 11.

235 x 5 = 1 175 Look below to see how it is done. Remember to line up the units, tens and hundreds underneath each other.

Now have a look at the sum:
255 x 25

First, multiply 255 by the unit digit 5.
Step 1: 5 x 5 = 25. Put the 5 in the units column, and carry the 2 to the tens.
Step 2: 5 x 5 = 25. Add the 2 makes 27.
7 goes into the tens column and carry the 2 to the hundreds column.
Step 3: 5 x 2 = 10. Add the carried 2 makes 12.

Then multiply 255 by the tens digit 2.
Remember to add a zero first when multiplying the tens.

Step 1: 2 x 5 = 10. Put the 0 in the tens column, and carry the 1 to the hundreds.
Step 2: 2 x 5 = 10. Add the carried 1 makes 11.
1 goes into the hundreds column, with 1 carried to the thousands.
Step 3: 2 x 2 = 4, add the carried 1 makes 5. The total is 5 100.

Finally, add down the columns down to get the total. Have a look below to see how it is done.

255 x 25 = 6 375

Remember:

• Keep the numbers in columns - units, tens, hundreds etc
• When multiplying the tens digit add a zero first.