Lego Ninjago and Rounding off to nearest 20

One of Avi’s tooth fell and he got 5 bucks from tooth fairy. This put him a little closer to having enough for a Lego Ninjago set that he really wanted. So I told him that we could go to Vons and get money for all the coins he has saved in his money bank.

Yesterday, when I checked his homework folder, I saw a few practice problems that he worked on which involved rounding off to the nearest 10 or 100. This gave me an idea. While coming back from swimming and while going to Vons to exchange all the coins, I asked him if he wanted to make a deal. I said that whatever money he gets from his coin bank, I’ll round it to the nearest 20. I told him that it’s a risk for him, because if he gets $9 or $29, he’d be getting $0 or $20, which means he’d be losing money. But if he gets $11 or something like that, he’d get $20 and basically more money that he actually had. He thought about it a little and after a little prodding, said yes.

I could see that he was a little antsy when the machine started displaying the value because most of the coins he had in his money bank were pennies. It went up to 8 dollars and then it just was increasing penny by penny. The final amount he got was 8.44. Not enough to round to $20 so he’d end up with 0. I could see that he was getting sad and asked him if he knew what it meant. He said that it meant he’d get $20. I asked him what the nearest 20 value is to 8.44 and after a little repetition, he admitted that it is $0. I knew from the start that if it comes out to this, I’d give him the 20 bucks, but there’s 2 things that I wanted him to learn:

1. Taking risks: It was almost a gamble for him but he should be willing to take a few risks in his life. I hope this didn’t discourage him and also that it taught him about the risk/reward aspects of such a gamble.

2. Rounding off: When putting in the context of real money that he was hoping to use to buy a much wanted toy, I think it helped him learn better how rounding off to a nearest value works.