Doubling Numbers

Doubling is often one of those maths concepts that everyone assumes everyone can do. However, you'd be surprised at the number of Primary / Elementary students that find this difficult or have just never bothered to learn. In my experience it is so important in building basic mathematical knowledge and giving children number knowledge they can build on.

When doubling with your child I would recommend starting with the basic numbers: 1, 2, 3, 4, 5, 6, 7, 8 and 9. Starting easy builds confidence and ensures you have checked they know their doubles.

Here is a mini 'Lesson Plan' for you to work through with your child.

Start with a quick warm up. Use one of the number activities and choose a sequence of numbers to work with. Depending on the level of your child you could just count. This could be anything from 0 - 20 or 150 - 180. Do one or two of the activities with either the same set of numbers or two different sets. Make it fun, have a giggle and get both of you in the right frame of mind for learning something.

Briefly talk about doubles. Ask your child what doubling means and the throw some examples at him / her.

I would suggest using the units to start with (1, 2, 3, 4, 5, 6, 7, 8, 9)

If this is the level you need to work at then I would suggest you use some of the number activities and practice doubling all the units over again until your child is done practicing or can do them. Throwing and catching a ball is really good for this as you can give the unit and then your child can double it. This will need to be revisited several times before you can safely say he / she is confident with them.

If you find single digits are too easy then use higher numbers. Keep getting higher until your child is having to think about the numbers and then play some games and practice. (This can be great fun with really high numbers too, so parents of high ability children go for it, push the numbers harder and harder)

Once your child has mastered doubling the units I always found it useful to show students a visual that can help them double 2, 3,4 or more digit numbers.

Start with something fairly easy so they're not having to think too much about the numbers.

Write your number down and then draw little arrows from each digit and underneath each arrow write what the double of that part of the number is.

                       12

                      /   \

                   20     4

                     \     /

                       24

Then draw arrows underneath these doubles to show putting these numbers together and the answer you will get.

It is important initially to make sure that when you double the tens digit you don't just write an individual number but the correct double. So for the above example you need to write 20 and not 2. This ensures your child is clearly understanding how doubles work. If you used 2 then you risk the answer being 6 if your child is a little unsure on place value and how that works.

If you're starting to double 3-digit numbers then use the same visual as above but with three numbers and please remember to keep all the zero's in the numbers to ensure full understanding of place value.

Hopefully by using this visual your child will soon be able to do this in their head using the visual which just helps them to break the numbers down and quickly work out that double.

Do some more examples with the visual with your child until they have clearly mastered it. Once they've done this you will need to alternate for a while between using the head and using the visual on paper to consolidate. For example you could play a variety of games over the next couple of days. Just do a game for 5 minutes or so and then leave it and do another game later that day or the next day for another five minutes or so.

Some games you could play:

Have a race - see who can double a number first, on paper or in your heads.

When driving along every time one of you spots a number somewhere call it out and the rest of the car have to double the number.

Start a number sequence by alternating between you (throwing a ball or marching etc) but the sequence is doubling eg. 2, 4, 8, 16, 32........

Once doubling is a secure skill that your child has you will be able to very quickly build this knowledge to doubling higher numbers. It is something that you will need to keep revisiting for a while as you gradually increase the numbers. At some point you will suddenly realise that your child can do this and no matter what numbers you throw at them (within reason) they can double them.