Magnetism and maths with money

My son loves to 'beep' my contactless card when we are shopping to pay for things, but he rarely handles coins. As a result he doesn't know what the value of each coin is and wouldn't know how to go about finding the right combination to pay for something. He does, however, get quite excited by opportunities to use cash e.g. buying milk from the corner shop when we have run out, or putting a pound coin in the locker at the swimming pool. I thought he might therefore enjoy a couple of activities aimed at familiarising him with our coins whilst playing with some science and maths.

The first thing we did was magnetic sorting. He's enjoyed sorting things with a magnet before and was keen to do what I had planned when he saw the big horseshoe magnet. I'd carefully selected a sample of coins which included each denomination (except £2) and which ranged widely in the year they were minted. Why did having a spread of age matter? UK coins have changed in metal content over the years such that some of the same value and shape are magnetic but others are not.

His first activity was to sort the coins into groups of the same size/colour (i.e. the same value) and then to check whether they were magnetic. He wasn't very engaged by the shape and colour sorting and not at all keen on trying to find where on the coins it said how many pence they were worth. He recognised the pound, but no other coins. I gave up trying to coax him to look for the numbers/words (which in fairness aren't very easy to find) and moved on to sorting using the magnet.

Investigating whether coins are magnetic

My son was far keener on magnetic sorting and started with enthusiasm.  He first tried a 2p coin and found it stuck to the magnet.  He then assumed that all the 2p coins would stick and told me the whole pile was magnetic.  When I asked him if he was sure, he checked each one in turn and found than some of them didn't stick.  Why?  The metal content of the 2p coins (as well as 1p coins) changed from an alloy of copper, tin and zinc (bronze) to copper-plated steel in September 1992, and only those which contain steel are magnetic.  According to the Royal Mint, the coins are the same colour, weight and size, so are otherwise indistinguishable.  The year the coins were made is on them, so you can pick some from before and after this date if you want to try this activity - I found some in my purse from 1979.  I explained that whilst the coins looked the same, they were actually made from different metals, and he told me that the ones which stuck to his magnet must contain iron.

Magnetic sorting almost complete

He then set out to sort the other coins. He found the same with the pennies as for two pence coins, namely that older ones aren't magnetic. The pound, fifty pence and twenty pence coins are not magnetic, and I didn't let him loose with many of them so he sorted those quickly. He was surprised to find a 10p stuck to his magnet, and when I asked why he was surprised he said it was because the other silver coins (i.e. the 50p and 20p) hadn't been magnetic. Again, it turns out that our coins changed metal content to a presumably cheaper plated steel. This happened later than for the coppers, in 2011. I'd picked coins either side of this date and he sorted them according to whether they were attracted to his magnet. Whilst he enjoyed playing with the coins and magnet, and it was fun to watch him discover unexpected results, it gave a nice opportunity to talk about the value of the coins, by referring to their value as we discussed what he'd found. He used the correct values a few times when telling me about them too.

Over the past few weeks, inspired by a cardboard shop at a friend's house which he enjoyed playing with, we have played 'shop' several times. We turned a cardboard box into a makeshift shop counter akin to the one he'd played with, although a lot less pretty and stable, and had a lot of fun with it. He loves to be the shopkeeper and for me to be his customer (although he likes to tell me what I should buy...). We use our Numicon for money, and everything is priced in round pounds, so he tells me what to buy, I ask what it costs, and then pay. I started our giving him exact change, but then found that he enjoyed working out the change if I gave him too much (I usually made it easy e.g. giving him 10, when he's pretty familiar with number bonds to 10, or just giving him one more than the price). It's been a nice play and maths activity, but I wanted to try and extend it to use real coins.

Toy food in my 'shop'

I have been trying to talk to him more when we are shopping in physical shops about how much things cost, to start to give him an idea of the value of money e.g. what a pound will buy. I therefore took some of the toy food we have played shop with and made some price stickers from some labels with prices on which roughly reflect the cost in real life. I picked numbers which can't be made with single coins so he would have to think about which combinations of coins he needed. I made it a bit too difficult in hindsight, and he needed help with the addition, but it started well. He chose a tomato (cost 7p) and started to try and make 7p with 2p coins. He got to 8p and realised he needed something different so I helped him find a penny to make the right amount. He then picked a pineapple (£1.30, rather hilariously after saying he didn't like pineapple for months, whilst refusing to try it, he discovered a couple of weeks back that it's really nice and he keeps asking for it now!) and found the pound coin. He couldn't remember what the value of the silver coins was so I reminded him and helped him to make 30p from a 20 and 10. I was possibly a bit too overenthusiastic about helping him, and I think he would have made the 30 with three 10p coins if I'd left him without prompting for longer. He then decided he wanted the aubergine and cheese so we found the right coins together. And then he just had 11p left and the cheapest item left cost 12p.

'Buying' a tomato and pineapple

Not enough money left to buy everything

I hadn't really thought through that we would run out of money (which is pretty stupid in hindsight) but I asked him if he wanted to swap something for an item he'd already paid for. He was adamant that he wanted all of the items, thought for a moment and said that he'd go to work to earn some money! Whilst amused, I was quite pleased that he's got the idea that money doesn't grow on trees... Anyway, I asked what job he was going to do, and he was a bit non-specific about it. I found some more pound coins and a £2 coin and said that was what he was being paid for his work, so that we could continue playing! He lost interest after having a good look at the £2 coin, so he never did buy the rest of the groceries!