1. Halving And Doubling
for mental maths
By Ben Pickford

2. Step one
If you have a hard mental maths sum e.g.25x48 you could use the halving and doubling method (as long as one of the numbers is even).
You start by halving the 48 and doubling the 25.
25x2=50
48/2=24
Like this

3. Step two
If you don’t want to do a sum like 50x24 you could do the same method again.
Like this.
50x2=100
24\2=12
50 x 24…
25 x 48 =

4. Step three 100x12=1200 So the answer is 1200
Finally, when you are happy - you do the sum in your head...
Like this
100x12=1200
25 x 48 =
50 x 24 =
100 x 12 =
So the answer is 1200

5. Here is a summary of the steps...
Starting with 25 x 48...
3) 100x12=1200 so
25 x 48 = 1200
2) 50x2=100
24\2=12
1) 25x2=50
48/2=24
Here is a summary of the steps...

6. Now you can have a go at these…
1) 45 x 18
2) 35 x 24
3) 55 x 6
Click to continue…

7. The answers… 90 x 9 = (9 x 9) x 10= 810 ! 70 x 12 = (7 x 12) x 10
=840 !
3) 55 x 6 =
110 x 3 =
(11 x 3) x 10
= 330

8. I hope you enjoyed my show!
Remember to halve,
double and make use
of your times tables!
The end… (for now)!