L.O.1
To be able to use known facts and place
value to multiply and divide mentally.
Answer these on your whiteboards:
What are 10 lots of 5?
What is the product of 20 and 5?
What is 30 multiplied by 5?
What are 10 lots of 6?
What is the product of 20 and 6?
What is 30 multiplied by 6?
As 20 is double 10
so 20 x 6 = double 10 x 6
20 x 6 = 2 x (10 x 6)
= 120
As 30 is treble 10
so 30 x 6 = treble 10 x 6
30 x 6 = 3 x (10 x 6)
= 180
As 40 is quadruple 10
so 40 x 6 = quadruple 10 x 6
40 x 6 = 4 x (10 x 6)
= 240
As 50 is quintuple 10
so 50 x 6 = quintuple 10 x 6
50 x 6 = 5 x (10 x 6)
= 300
Q. How many 6’s are there in 120?
How do you know?
120 = 12 x 10
so 120 ÷ 6 = (12 ÷ 6) x 10
= 2 x 10
= 20
What are the answers to these?
180 ÷ 6
240 ÷ 6
300 ÷ 6
360 ÷ 6
420 ÷ 6
480 ÷ 6
540 ÷ 6
LOOK…
180 ÷ 6
240 ÷ 6
300 ÷ 6
360 ÷ 6
420 ÷ 6
480 ÷ 6
540 ÷ 6
=
=
=
=
=
=
=
(18÷6) x 10
(24÷6) x 10
(30÷6) x 10
(36÷6) x 10
(42÷6) x 10
(48÷6) x 10
(54÷6) x 10
=
=
=
=
=
=
=
3 x 10
4 x 10
5 x 10
6 x 10
7 x 10
8 x 10
9 x 10
=
=
=
=
=
=
=
30
40
50
60
70
80
90
What are the answers to these?
1. 240 ÷ 4
2. 250 ÷ 5
3. 180 ÷ 2
4. 200 ÷ 4
5. 280 ÷ 7
6. 540 ÷ 9
7. 160 ÷ 2
8. 320 ÷ 8
LOOK…
1. 240 ÷ 4
2. 250 ÷ 5
3. 180 ÷ 2
4. 200 ÷ 4
5. 280 ÷ 7
6. 540 ÷ 9
7. 160 ÷ 2
8. 320 ÷ 8
=
=
=
=
=
=
=
=
(240÷4)
(250÷5)
(180÷2)
(200÷4)
(280÷7)
(540÷9)
(160÷2)
(320÷8)
=
=
=
=
=
=
=
=
6 x 10
5 x 10
9 x 10
5 x 10
4 x 10
6 x 10
8 x 10
4 x 10
=
=
=
=
=
=
=
=
60
50
90
50
40
60
80
40
L.O.2
To be able to approximate;
extend written methods to short
division of HTU by U;
estimate by approximating
then check results.
We are going to use a shorter written method for division.
183 ÷ 5
Q. Approximately how many fives are there in
183?
183 ÷ 5
We know that
We know that
30 x 5
40 x 5
=
=
150
200
so as 183 comes between 150 and 200
our answer lies somewhere between
30 and 40
Using chunking…
Watch carefully!
We can start by using the LOWER of our two
estimates…
183
150
33
30
3
( 30 x 5)
( 6 x 5)
Answer = 36 r.3
Q. Is 36 r.3 likely to be correct? How do you know?
Try this on your own. When you have an
answer compare it to your partner’s.
147 ÷ 6
There is a similar method called short division.
Our sum is 183 ÷ 5
CHUNKING
183
-150 (30 x 5)
33
- 30
(6 x 5)
3
Answer = 36r.3
How are these sums similar?
SHORT DIVISION
36r.3
5 183
- 150 (30 x 5)
33
- 30
(6 x 5)
3
How are they different?
Try these:
Use the SHORT DIVISION method.
Approximate the answers first.
Use the LOWER multiple of the divisor as the first subtraction.
1. 154 ÷ 5
2. 176 ÷ 5
3. 188 ÷ 5
4. 237 ÷ 4
5. 169 ÷ 6
6. 222 ÷ 6
Answers??
1. 154 ÷ 5
2. 176 ÷ 5
3. 188 ÷ 5
4. 237 ÷ 4
5. 169 ÷ 6
6. 222 ÷ 6
Q. Do the answers seem to be correct compared to the
approximations?
Check your own answers. Where have you gone wrong?
By the end of the lesson the children should
be able to :
Use short division to divide HTU by U;
Approximate results first and use the
approximation to check whether results
are reasonable