# long - multiplication .ppt

Document Sample

```					       Oh no! I can’t do long
multiplication. What
am I going to do?

Don’t panic!
Take it step by step
example.
23 x 14

When multiplying these two numbers
together, it is easier to put
them into a grid.
The first thing to do is
23 x 14    partition the numbers into
tens and units.

20          3

10

4
Multiply the number above

23 x 14
the box with that on the left,
writing the answer inside the box,
as shown below.

20              3

10   200             30

4    80              12
The next step is to add up
23 x 14   the rows, putting the answer
in the boxes on the right.

20      3

10    200      30           230

4      80      12            92
Now add up the totals on the
23 x 14    right to give the answer.

20      3

10    200      30           230

4      80      12            92

322
Now you can work out multiplication
using the grid method, you will find long
multiplication easy!

This is a little different
from the grid method,
as the numbers are
set out in columns…
51 x 42
becomes
51
x 42
Remember what

51 x 42                      51
we did using
the grid method?

x 42
The first thing to do, is
multiply the tens of the
top number with the tens
and units of the bottom
number.
51 x 42                      51
x 42
50 x 40           2000
50 x 2             100

Always write down the
multiplication you have
worked out next to
Next, multiply the

51 x 42         51
units of the top
number by the tens
and units of the
x 42  bottom number.

50 x 40    2000
50 x 2      100
Don’t forget to

51 x 42         51
write down the
multiplication
next to the

50 x 40    2000
50 x 2      100
1 x 40      40
1x 2         2
The final step is

51 x 42         51
column of
numbers and put
x 42      the total at
the bottom.

50 x 40    2000
50 x 2      100
1 x 40      40
1x 2         2
2142
Try using long multiplication
to work out…

25 x 62
25 x 62
becomes
25
x 62
25 x 62                       25
x 62
x
x
Remember:
The first step is to multiply the
tens of the top number with the
tens and units of the bottom
number.
25 x 62          The next step is to

25multiply the units
of the top number
x 62  by the tens and
units of the bottom
20 x 60    1200     number.

20 x 2       40
x
x
25 x 62           25
the totals
and put
x 62    them at the
bottom.
20   x 60    1200
20   x 2       40
5   x 60     300
5   x 2       10
25 x 62           25
x 62
20   x 60    1200
20   x 2       40
5   x 60     300
5   x 2       10
1550
You can now work out
calculations using
long multiplication.

```
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