My father buys things in bulk. Not the bulk bin, dispense-a-little-bit-into-a-plastic-bag bulk. Costco bulk. Sam’s Club bulk.
The children and I spent some time with my father and stepmother (who are wonderful, loving people) at the Wisconsin Dells recently. We shared a rented condo. They brought bulk snacks.
Did you know that you can buy graham crackers in a container that holds four of the usual boxes of graham crackers?
What need does one family have with FOUR BOXES of graham crackers?
More to the point, they brought pistachios. I forget to check whether it was a three-pound bag or a four-pound bag but it was an awfully large bag of pistachios.
The image below is a small fraction of the total.
While we were in the condo, Tabitha (7 years old) took her first interest in pistachios. Her brother Griffin (nearly 10 years old) has been a fiend for them for years. One day, Tabitha announced something to me.
Tabitha (7 years old): I threw out eight pistachio shells.
Me: And what do you learn from that?
T: I ate four pistachios.
Me: How do you know that?
T: Four plus four is eight.
Me: Nice. And five plus five?
We carried on this vein for a little bit before we got distracted.
A couple days later, I was rushing around preparing for a work trip. Tabitha was again snacking on pistachios.
T: Is 13 an even number?
Me: No. Why do you want to know?
T: I must have counted my pistachio shells wrong. I must have missed one. So it’s 14.
Me: And what does that mean in terms of pistachios?
T: I ate 12. No. That can’t be right.
Me: Oh! I think I know how you got 12!
At this point, I was headed downstairs to get something to put in my suitcase. By the time I got back up, both of our minds were on to different things.
We never did get to a solution, nor did I find out how she got her wrong answer.
So what do we learn?
Tabitha is playing around with the every pistachio has two shells relationship. She is thinking about ratios: Two shells for every one pistachio.
A child does not need to have mastered multiplication, or fractions, or division to think about these things. I have written about ratio thinking from young children before. Ratios come naturally from repeating a process. Eating a pistachio produces two empty shells every time. Sharing candy produces one piece of candy every time. And so on.
Starting the conversation
In light of this, help your child notice for every relationships. There are four wheels for every car. There are four legs for every chair. There are two wings for every bird. Point these relationships out and have your child do the same. Consider the exceptions (have you ever seen a 3-legged chair?) Count up how many wheels there are on two cars, and on three cars.
I have two theories about her answer of 12 pistachios for 14 shells.
1. She tried to figure it out by thinking about 10 and 4. Half of 4 is 2. She added that back to the 10 and forgot that she still needed to find half of 10.
2. She subtracted 2 from 14.
I like theory 1 a LOT better than theory 2 because it matches the ways she has been thinking so far. Using subtraction seems unlikely when she knows this is a different sort of problem.
But of course I do not know for sure.