multiplication using the lattice method including multiplication of decimals by estimation
TRANSCRIPT
Multiplication
Using the Lattice Methodincluding multiplication of decimals
by estimation
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 …
Cut each square diagonally in half.
Write the numbers to be multiplied around the top and right edges.
Use a highlighter pen to highlight every other diagonal stripe.
Multiplication Using Lattice Demo
4
5 7 2
1
Multiply the digits at the top and right of each cell and write the answer in the cell.
Multiplication Using Lattice Demo
0
5
0
7
5 7 2
1
4
0
2 2
0
2
8
0
8
Ten Thousands
Thousands
UnitsHundreds TensThe digits in each diagonal stripe all have the same
place value...
Add up each stripe. Write the total for each stripe at the end of the stripe.
5 7 2
Multiplication Using Lattice Demo
1
4
0
5
0
7
0
2 2
0
2
8
0
8
Ten Thousands
Thousands
UnitsHundreds TensNow we add up the digits,
starting with the units corner...
Add up each stripe. Write the total for each stripe at the end of the stripe.
5 7 2
Multiplication Using Lattice Demo
1
4
0
5
0
7
0
2 2
0
2
8
0
8 0 8 0
8
0
11
Always write down your answer ...
572 × 14 = 8008
Question 1 (with answer)
Calculate 76 × 21
7 6
2
1
1
5
9 76 × 21 = 1596
1
4
1
2 0
7
0
6 6
Question 2 (with answer)
Work out 152 × 34
1 5 2
3
4
0
3
1
5
0
6 0
4
2
0
0
8
0
5
6 81
1
152 × 34 = 5168
Question 3 (with answer)
Calculate 237 × 14
2 3 7
1
4
0
2
0
3
0
7 0
8
1
2
2
8
0
3
1 83
1
237 × 14 = 3318
1
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.
3 5
3
1
1
0
83.5 × 31 = 108.5
0
9
1
5 0
3
0
5 5
1What about the decimal point?4 × 30 = 120 so the answer is about 120
1 0 8 5
Decimal Multiplication(two decimal numbers)
Work out 15.6 × 7.4
1 5 6
7
4
0
7
3
5
4
2 0
4
2
0
2
4
1
1
4 45
1
15.6 × 7.4 = 115.44
What about the decimal point?10 × 8 = 80 20 × 8 = 160 so the answer is more than 80 and less than 160
1 1 5 4 4
1
Question 4 (with answer)
Calculate 9.37 × 1.2
9 3 7
1
2
0
9
0
3
0
7 1
8
0
6
1
4
1
1
4 42
1
9.37 × 1.2 = 11.244
What about the decimal point?10 × 1 = 10 so the answer is about 10
1 1 2 4 4
1
1
Question 5 (with answer)
Calculate 61 × 9.8
9 8
6
1
5
9
761 × 9.8 = 597.8
5
4
4
8 0
9
0
8 8
What about the decimal point?60 × 10 = 600 so the answer is about 600
5 9 7 81
Question 6 (with answer)
Calculate 7.5 × 0.3
7 5
0
3
0
2
2 7.5 × 0.3 = 2.25
0
0
0
0 2
1
1
5 5
What about the decimal point?8 × 0.5 = 4so the answer is about 4
2 2 5
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
Your Turn
End