Multiplication
Using the Lattice Method
including multiplication of decimals
What’s It All About?
You are going to learn:
How to multiply two whole numbers.
What skills should you have already?
You need to be able to multiply up to 9 × 9 and add
single digit numbers.
Multiplication Using Lattice Demo
Calculate 572 × 14
Draw a box.
You need
three squares across and
two squares down.
Because 5 7 2 has three
digits and 1 4 has two
digits …
Multiplication Using Lattice Demo
Cut each square diagonally in half.
Write the numbers to be multiplied
around the top and right edges.
5
7
2
1
4
Use a highlighter pen to highlight every other diagonal stripe.
Multiplication Using Lattice Demo
Multiply the digits at the top and
right of each cell and write
the answer in the cell.
5
Ten Thousands
Thousands
7
0
2
0
5
2
0
7
2
0
2
0
8
4
8
Hundreds Tens Units
The digits in each diagonal
stripe all have the same
place value...
1
Multiplication Using Lattice Demo
Add up each stripe.
Write the total for each stripe
at the end of the stripe.
5
Ten Thousands
Thousands
0
7
0
5
2
0
7
2
0
2
2
0
8
4
8
Hundreds Tens Units
Now we add up the digits,
starting with the units
corner...
1
Multiplication Using Lattice Demo
Add up each stripe.
Write the total for each stripe at
the end of the stripe.
5
0
7
0
0
5
8 21
1
0
0
Always write down your
answer ...
2
0
7
2
2
0
8
0
1
4
8
8
572 × 14 = 8008
Question 1
(with answer)
Calculate 76 × 21
7
1
1
1
5 0
6
2
4
0
7
9
6
6
2
1
76 × 21 = 1596
Question 2
(with answer)
Work out 152 × 34
1
0
0
5
0
1
3
0
1
5
4
1
2
6
5
0
2
0
6
3
4
8
8
152 × 34 = 5168
Question 3
(with answer)
Calculate 237 × 14
2
0
0
3
0
0
2
0
1
3 18
3
7
7
3
2
1
2
1
1
4
8
8
237 × 14 = 3318
Your Turn
1
532 × 65
2
63 × 51
3
234 × 97
4
7165 × 4
5
37 × 45
6
103 × 54
Decimal Multiplication
(one decimal number)
Calculate 3.5 × 31
First step is identical to whole numbers.
Second step – draw a line through the decimal point.
3  5
1
0
**Put the decimal
1
1
3
5
9
number at the top**
0
0
0
3
5
1
8  5
Decimal point goes
at the end of the line
3.5 × 31 = 108.5
Decimal Multiplication
(one decimal number)
Calculate 3.5 × 31
First step is identical to whole numbers.
Second step – draw a line through the decimal point.
3  5
Decimal point goes
1
0
at the end of the line.
1 1 9
3
5
0
0
0
5
3
8

5
1
Explain why this works.
35 × 31 = 1085
and so
3.5 × 31 = 108.5
Decimal Multiplication
(two decimal numbers)
Work out 15.6 × 7.4
If the lines
meet in the
middle of
the box then go
down the slide.
1
0
11
5
2
5
0
1
1
4
5
6
4
3
7

2
2
0

4
7

4
4
4
15.6 × 7.4 = 115.44
Decimal Multiplication
(two decimal numbers)
Work out 15.6 × 7.4
If the lines
meet in the
middle of
the box then go
down the slide.
1
0
11
5
Explain why this works.
2
5
0
1
1
4
5
6
4
3
7

2
2
0

4
7

4
4
4
156 × 74 = 11544
and so
15.6 × 7.4 = 115.44
Question 4
(with answer)
Calculate 9.37 × 1.2
9
0
1 1
1

9
11
18
2
3

7
0
0
7
3
1
0
6
4
1

2
4
4
9.37 × 1.2 = 11.244
Question 5
(with answer)
Calculate 61 × 9.8
9
5
4
5
9 10
8

8
4
0
8
9
7

6
1
Remember – put the
decimal at the top
8
61 × 9.8 = 597.8
Question 6
(with answer)
Calculate 7.5 × 0.3
7
0

0
0
2 2
5

0
0
1
1
2
5
0

3
5
7.5 × 0.3 = 2.25
Your Turn
1
53.4 × 65
2
6.3 × 6.1
3
2.34 × 45
4
1.65 × 4
5
3.8 × 4.2
6
1.03 × 5.6
End