Today turned out to be accidentally all about 10, mainly due to stamps. I say accidentally but there was some method, after all she had chosen 10 as our number of the week. The number of the week was initially her idea at the beginning of last term but jumped on by me and my nerd father who loves to talk numbers over dinner.
We have not long moved to Nelson so have a lot of people to remind of our existence by letter and I do so like getting mail back and I will keep it forever people. Recently we also had a “holiday” so made and wrote postcards. Postcards need posting. Stamps come in a range of denominations – in multiples of ten, with nice clear numbers on them and pretty pictures (You can get a 5c stamp which is interesting seeing as we do not have 5c pieces and I don’t know where to post to that costs something ending in 5). Postage is 1$ – 100 cents…. perfect. NO, not anymore, postage is now $1.20, which will be a great conversation later. We had brought lots of stamps of different denominations, I also found a stash of old christmas stamps that were 80c, and Helena started making piles on a white board making 100 as she saw fit and then got to put them on the envelopes and cards -we did some last term as well.
I had thought a little ahead and got out a surprisingly excellent book which has the number 0 telling us about the origin of numbers, place value and base 10.
We arrive at the post office, with our now wrong postage, and our post cards covered in stamps to find we need to squeeze in more stamps. Helena confidently said what value of stamps we would need and what we would now need to go with the stash of Christmas stamps. Lots of lovely skip counting in 10 in a real world context.
Since we started our stamp counting Helena has discovered reading prices, adding up all her coins, giving change and knowing what change or rather how much she will have left over when she buys something.
Then today we talked about the magic power of 10. We had a letter to Canada and some random stamps. Ones for $1.50, $.10 and 80c. We added this by adding the number of tens 15 + 1 + 8 = then we later talked about 1 x 10 = 10, 10 x 10 = 100, 100 x 10 = 1000… all you do when you multiply by 10 is add a zero. How CHOICE is that. Wait until I tell her that when you multiply by 100 you add two zeros.
That pile of stamps is $20.70 worth…