Multiplying Large Numbers

advertisement

Multiplying Large

Numbers (Traditional

Method)

Created by: Sabrina Edmondson

Adapted 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.

H T O

2

2 3 5 x 5

Step 1: 5 x 5 = 25.

Put the 5 in the units column, and carry the

2 to the tens.

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.

x

H T O

1 2

2 3 5

5

7 5

Multiplying Large

Numbers

Th H T O

Step 3: 5 x 2

= 10. Add the carried 1 makes 11.

x

1 2

2 3 5

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:

H T O

255 x 25

2 5 5 x 2 5

Multiplying Large

Numbers

H T O 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 x

2

2 5 5

2 5

5

Multiplying Large

Numbers

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. x

H T O

2 2

2 5 5

2 5

7 5

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.

x

Th H T O

2 5 5

2 5

1 2 7 5

0

Multiplying Large

Numbers

Th H T O

Step 1: 2 x 5 =

10. Put the 0 in the ten’s column, and carry the 1 to the hundreds . x

1

2 5 5

2 5

1 2 7 5

0 0

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. x

Th H T O

1 1

2 5 5

2 5

1 2 7 5

1 0 0

Multiplying Large

Numbers

Th H T O

Step 3: 2 x 2 = 4, add the carried 1 makes 5. The total is 5,100. x

1 1

2 5 5

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 O

1 1

2 5 5 x 2 5

So: 255 x 25 = 6,375

1 2 7 5

5 1 0 0

6 3 7 5

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.

Download