Long Multiplication Slidecast

Long Multiplication

By Mr. Kish

Pros and Cons

Pros

• Likely faster than partial products

• Works everytime• Better understood by

most people (e.g. parents)

Cons

• It isn’t clear why it works

• Some steps can be forgotten

• Some students have a hard time mastering

An example of long multiplication

x

6 35 4

An example of long multiplication

x

Make an estimate

6 35 4

An example of long multiplication

x

Make an estimate

60 * 50

6 35 4

An example of long multiplication

x

Make an estimate

60 * 50 = 3,000

6 35 4

An example of long multiplication

x

6 35 4

An example of long multiplication

x

2

6 35 4

An example of long multiplication

x

2

1

6 35 4

An example of long multiplication

x

252

1

6 35 4

An example of long multiplication

x

252

1

0

6 35 4

An example of long multiplication

x

252

1

50

1

6 35 4

An example of long multiplication

x

252

1

3150

1

6 35 4

252

An example of long multiplication

x

1

3150

1

+

6 35 4

252

An example of long multiplication

x

1

3150

1

+

3042

6 35 4

An example of long multiplication

x

Make an estimate

9 16 2

An example of long multiplication

x

Make an estimate

90 * 60

9 16 2

An example of long multiplication

x

Make an estimate

90 * 60 = 5,400

9 16 2

An example of long multiplication

x

2

9 16 2

An example of long multiplication

x

182

9 16 2

An example of long multiplication

x

1820

9 16 2

An example of long multiplication

x

18260

9 16 2

An example of long multiplication

x

1825460

9 16 2

182

An example of long multiplication

x

5460+

9 16 2

5642

182

An example of long multiplication

x

5460+

9 16 2

A more complex example

6 2 4x 3 3 1

A more complex example

6 2 4x

6213 3 1

18720187200+

206,544