Halving And Doubling

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Halving And Doubling
for mental maths
By Ben Pickford
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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.

25x250 48/224

• Like this

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Step two

• If you dont want to do a sum like 50x24 you
  could do the same method again.

• Like this.

50x2100 24\212
50 x 24
25 x 48
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Step three

• Finally, when you are happy - you do the sum in
  your head...

• Like this

100x121200
25 x 48
50 x 24
100 x 12

• So the answer is 1200

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Starting with 25 x 48...
3) 100x121200 so 25 x 48 1200
2) 50x2100 24\212
1) 25x250 48/224
Here is a summary of the steps...
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Now you can have a go at these
1) 45 x 18
2) 35 x 24
3) 55 x 6
Click to continue
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1) 45 x 18 90 x 9 (9 x 9) x 10 810 !
The answers
2) 35 x 24 70 x 12 (7 x 12) x 10 840 !
3) 55 x 6 110 x 3 (11 x 3) x 10 330
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I hope you enjoyed my show!
Remember to halve, double and make use of your
times tables!
The end (for now)!