Post on 01-Apr-2015
Multiplying Large Multiplying Large Numbers (Traditional Numbers (Traditional
Method)Method)
Multiplying Large Multiplying Large Numbers (Traditional Numbers (Traditional
Method)Method)Created by: Sabrina EdmondsonCreated by: Sabrina Edmondson
Adapted from BBC onlineAdapted from BBC online
Multiplying Large Numbers
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.
Multiplying Large Numbers
Have a look at how the equation 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.
H T O2
2 3 5
x 5
5
Multiplying Large Numbers
Step 2: 3 x 5 = 15. Add the 2 makes 17. 7 goes into the ten’s column and carry the 1 to the hundred’s column.
H T O
1 2
2 3 5
x 5
7 5
Multiplying Large Numbers
Step 3: 5 x 2 = 10. Add the carried 1 makes 11.
Th H T O
1 2
2 3 5
x 5
1 1 7 5
So: 235 x 5 = 1,175
Multiplying Large Numbers
Remember to line up the ones, tens and hundreds underneath each other.
Multiplying Large Numbers
Now have a look at the equation:
255 x 25
H T O
2 5 5
x 2 5
Multiplying Large Numbers
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
H T O
2
2 5 5
x 2 5
5
Multiplying Large Numbers
H T O
2 2
2 5 5
x 2 5
7 5
Step 2: 5 x 5 = 25. Add the 2 makes 27.7 goes into the tens column and carry the 2 to the hundred’s column.
Multiplying Large Numbers
Step 3: 5 x 2 = 10. Add the carried 2 makes 12.
Th H T O
2 2
2 5 5
x 2 5
1 2 7 5
Multiplying Large Numbers
Then multiply 255 by the ten’s digit 2.Remember to place a zero in the ones column first when multiplying the tens.
Th H T O
2 5 5
x 2 5
1 2 7 5
0
Multiplying Large Numbers
Th H T O
1
2 5 5
x 2 5
1 2 7 5
0 0
Step 1: 2 x 5 = 10. Put the 0 in the ten’s column, and carry the 1 to the hundreds.
Multiplying Large Numbers
Step 2: 2 x 5 = 10. Add the carried 1 makes 11.1 goes into the hundred’s column, with 1 carried to the thousands.
Th H T O1 1
2 5 5
x 2 5
1 2 7 5
1 0 0
Multiplying Large Numbers
Step 3: 2 x 2 = 4, add the carried 1 makes 5. The total is 5,100.
Th H T O1 1
2 5 5
x 2 5
1 2 7 5
5 1 0 0
Multiplying Large Numbers
Finally, add down the columns down to get the total.
Th H T O1 1
2 5 5
x 2 5
1 2 7 5
5 1 0 0
6 3 7 5
So: 255 x 25 = 6,375
Multiplying Large Numbers
Remember: Keep the numbers in columns - ones, tens, hundreds etc. When multiplying the tens digit add a zero to the ones column first.