Transcript Little bites at big multiplications

Little Bites at Big Multiplications
I am learning to solve multiplication and division problems using factors
of factors.
e.g. 8 X 9 = ?
(2 X 2 X 2) X 9 = ?
Let’s see how factors can be used to work out 6 X 5 = ?
Both 3 and 2 are factors of 6 (2 X 3 = 6).
Below is a fly strip with 5 faces.
Let’s multiply this amount by 2 (2 X 5 = 10).
Now let’s multiply this amount by 3 (3 X 10) = 30.
2 X 5 = 10
3 X 10 = 30
So 2 X 3 X 5 = 30
is the same as
6 X 5 = 30
Now let’s use factors to work out 8 X 5 = ?
2 is a factor of 8 (2 X 2 X 2 = 8).
Below is a fly strip with 5 faces.
Let’s multiply this amount by 2 (2 X 5 = 10).
Now let’s multiply this amount by 2 (2 X 10) = 20.
Now multiply this amount by 2 (2 X 20) = 40.
2 X 5 = 10
2 X 10 = 20
So 2 X 2 X 2 X 5 = 40
is the same as
8 X 5 = 40
2 X 20 = 40
Now let’s use this method to work out a more difficult question.
12 X 52 = ?
3 X 2 X 2 = 12 so I could use these as factors.
3 X 52 = 156
2 X 156 = 312
2 X 312 = 624
So 12 X 52 = 624
We can also use factors to help us work out division questions.
64 ÷ 8 = ?
First we must find the factors of 8. 2 X 2 X 2 = 8
64 ÷ 2 = 32
32 ÷ 2 = 16
16 ÷ 2 = 8
So 64 ÷ 8 = 8
Now lets use this strategy for a more difficult division question.
180 ÷ 12 = ?
First we must find the factors of 12. 2 X 3 X 2 = 12
180 ÷ 2 = 90
90 ÷ 3 = 30
30 ÷ 2 = 15
So 180 ÷ 12 = 5
Use this strategy to work out answers to the questions below
Click again when you have worked out all your answers.
1) 8 X 23 = ?
184: 2 X 23 = 46, 46 X 2 = 92, 92 X 2 = 184
2) 12 X 14 = ?
168: 2 X 14 = 28, 28 X 2 = 56, 56 X 3 = 168
3) 216 ÷ 12 = ? 18: 216 ÷ 2 = 108, 108 ÷ 2 = 54, 54 ÷ 3 = 18
4) 128 ÷ 8 = ?
16: 128 ÷ 2 = 64, 64 ÷ 2 = 32, 32 ÷ 2 = 16
279: 3 X 31 = 93, 93 X 3 = 279
5) 9 X 31 = ?
Need some more practise? Try Pg51 & 52 of Teacher Tools Multiplication
and Division Book Numeracy resources