Maths Update: Adding/Subtracting 2-digit numbers

After revising partitioning, we recapped how to add 2-digit numbers mentally, i.e. partition into Tens and Units, add the Tens, add the Units, add both parts together. They also had the option of adding the Tens from one number to the other, then counting up the remaining Units, e.g.

28 + 43 =

20 + 40 = 60
8 + 3 = 11

60 + 11 =

60 + 10 = 70
0 + 1 = 1

70 + 1 = 71 so 28 + 43 = 71

OR

28 + 40 = 68
68 + 3 = 71 so 28 + 43 = 71

We concentrated on the first method first, to get them used to partitioning the numbers. Then we moved onto the second method as something more efficient.

After the mental practise, I introduced the column method to them as an efficient way of writing their working out down. It's the same principle, partitioning and adding each place value one at a time, but written in a compact way, e.g.

16 + 43 = 

   16
+ 43
   59

We started with numbers which didn't carry over into the next column, then once they were comfortable with the method I explained how to write the extra Tens underneath the Tens column - and to make sure they included them in their answer! e.g.

45 + 36 =

    45
 + 36
    81
    1

We also spoke about using a quick mental method to check their answers.

We did all the above through explanation and examples on the whiteboard first, then answering questions from a photocopied worksheet using the method we were focusing on at the time.

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Next, we recapped subtraction of 2-digit numbers via partitioning and counting down, e.g.

38 - 14 =

38 - 10 = 28
28 - 4 = 24 so 38 - 14 = 24

Where the numbers stayed within the Tens, then using numbers in the Unit column which meant counting down across Tens, e.g.

52 - 26 = 

52 - 20 = 32
32 - 6 = 26 so 52 - 26 = 26

After some practise doing this mentally, I then introduced the column method to them - but for numbers which wouldn't require carrying, e.g.

88 - 43 =

    88
  - 43
    45

I decided that was enough for now, so they could get used to the method, and we would look at carrying from the Tens column at a later point inshaAllah!

The above was all done, one method at a time on separate days, first on the whiteboard and then in the context of numbers by working through practise pages from one of the workbooks we have.

Finally, I gave them some word problems to work through so they could use these skills in the context of money. They had the choice to use either a mental or a written method, whichever they found easier.

Maths update: Money

* The girls are now familiar with the different denominations of coin and can recognise them by size, shape and colour even if they can't see the number. They also know the common denominations of note (i.e. £5, £10, £20).

* They can find a variety of ways of making the same total by using different combinations of coins.

* They know that the number of coins and the worth of the coins can be two different things, i.e. three 5p coins are worth less than one 20p coin.

* They can solve simple addition and subtraction problems involving money as both numerical sums and word problems.

* They understand how to find the total price for items on a shopping list by referring to a price list.

* They can calculate the money leftover in their purse after buying something and the change they would be given depending on what they spend.

* They know the meanings of the words: cheap, expensive, good/poor value for money, quality.

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We learnt the above through a combination of conversations (especially while out shopping), playing with real coins, playing with toy money, role play as customers/shop keepers (we built a shop out of Duplo and wrote out a price list for the things inside), completing worksheets.

The toy money we had was on sale a while ago and I bought it without thinking... Upon opening it, it turned out all the coins were the same grey colour. 😒 Although all the correct denominations were there along with notes... So after looking at some real money from my purse, I asked the girls what was wrong with the toy money we had? Some of the coins were the wrong colour! To which F then said, "We can just paint them brown and gold." 😍

So we did. 👍

And the toddler did a painting of her own while the elder two were busy painting coins. 😀😀

Another time, when we were completing a worksheet using the coins to help visualise the answers, the toddler wanted to join in... So I just gave her the task of matching up all the coins which were the same.

It kept her busy (until she became bored and went to play with Lego instead!) whilst at the same time not getting in her sisters' way since it was actually helping them to find the coins they needed quicker... And she managed to do it too, MashaAllah, even if she didn't know what each coin's worth was. It was still famliarising herself with the different coins. 👍