Transcript Parents Guide to Long Multiplication

Parents Guide to Long
Multiplication
This Power Point Presentation will
Show Parents the Language We Use
When Teaching Children Long
Multiplication
Introducing Long
Multiplication
We introduce long multiplication
first of all by looking at
multiplying by 20, 30, 40 etc.
Example
54
62
X20
x30
Always multiply by the
units first:
54
X 20
We say, “54 multiplied by zero.”
Then we say, “54 multiplied by 2.”
Multiplying by 20
5 4
x 20
We introduce this calculation by saying:
54 multiplied by zero is zero.
When we multiply by zero the answer is always zero!
Put your zero in the answer.
Now we multiply 54 by 2.
We say 2 fours are 8. Put down your 8.
Now we say 2 fives are 10.
This is the end of the sum so put down the 10 in the
answer.
10
8
0
Example 2
4 6
x 20
We introduce this calculation by saying:
46 multiplied by zero is zero.
When we multiply by zero the answer is always zero!
Put your zero in the answer.
Now we multiply 46 by 2.
We say 2 sixes are 12. Put down your 2 and carry
your 1.
Now we say 2 fours are 8 add 1 is 9.
This is the end of the sum so put down the 9 in the
answer.
9
2
0
1
Remember: when we multiply by zero, the answer is always zero!
Try These:
52
X 20
48
X 40
29
X 30
95
X 40
34
X 20
83
X 30
94
X 40
28
X 50
34
X60
Long Multiplication
32
X 23
Step 1
Step 2
Step 3
32
X3
96
32
X 20
640
96
+640
Long multiplication is really 3 sums in one!
Step 1: multiply the top number by the units digit in the bottom number.
Step 2: Multiply the top number by the tens digit in the bottom number.
Step 3: add your two answers.
Be careful with your place value!
To remind us to keep the figures in the correct place, we talk about the
magic 0!
46
X23
138
Multiply 46 by 3
920
Put in your magic nought! Now do 46 multiplied by 2
1058
Finally add your two answers together!
Notice that without your magic nought the digits 9 and 2 would not
be in the correct place & your answer would be incorrect.
Now try these:
76
X23
82
X46
93
X54
32
X 41
46
X 54
64
X 32
Remember: Long multiplication is really 3 sums in one!
Step 1: multiply the top number by the units digit in the bottom number.
Step 2: Multiply the top number by the tens digit in the bottom number.
Step 3: add your two answers.
Click Below to Return to
Our School Website.
We hope this powerpoint will help you to
work with your child at home.
Please ask in school if you have any
questions regarding our approach to
teaching maths.
http://www.killeanps.com