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apples and oranges

It's friday, we're in the kitchen. Dinner is nearly ready.

- so Dad. Dad, once I can figure out the problem, I can do the sums. It's the problem that's hard. The first bit.

- I don't think I understand. Can you show me a problem in your homework book?

- Yes. The book's in my bag. I'll get it.

She runs off to the hallway, comes back with a math book opened to the last page.

- This, one, look. Number nine.

- Ok, let's see. "if you have to drive 9 1/4 Km and you've driven 5km and 585m, have far do you have left to drive?"

- That one. How you do that? I mean, I can do it. It's take away. But how do you figure out what to do?

- Ok. They're trying to test you on a few things here. The first thing that you have to do is get these two numbers into the same form. If you can the make numbers like each other, then you can take one away from the other and that will give you the answer. Both of the numbers have kilometers, but one has a meters bit and the other has a quarter.

- A quarter is fraction of a kilometer. We did fractions last year.

- Right. We can make these numbers the same in a few different ways. Which do you think is easier to subtract, meters or quarters?

- Meters

- Then how many meters is a quarter of kilometer? No, first. How many meters are there in a kilometer?

A pause.

- 1000.

- Good. What's a -

- Quarter of 1000. That's 250 meters.

- That's right. So one thing they're testing you on is whether you know how many meters are in a kilometer. Without that you can't make the numbers the same. Anyway. Now, how many meters are there in 9 kilometers?

- 9000.

- and what's 9000 and 250?

- there's 9250 meters.

- Yes. how many meters in 5 kilometers?

- 5000. And 585 is 5585 meters. I need to... take... 5585 meter from 9250 meters?

- Exactly. Now, do see what you need to do? When you have two amounts that aren't written down the same way you have to find out how to write them down the same way. That can be hard sometimes, but the pattern they're trying to teach you is to when you have to work with two different kinds of numbers is to find out how they can be made into the same types of numbers. Which is what you did just now. You turned everything into meters.

- Ok...

- A lot math is about seeing what the patterns are underneath the numbers. Once you know patterns, you can solve problems without worrying too much about what the numbers are.

- Ok...

- Now here's one. How would take away 3 apples from 5 oranges?

- immediately - You need to find out what fruit is.

She runs off to play guitar hero with her brother. Her mother, who has been half-listening all along, turns around, and says,

- I had no idea. I was going to say you can't take apples away from oranges.

- So was I. I'd never think of turning them into fruit.

- Dinner'll be ready in minute. Tell them to come in.

- Cool.

February 10, 2007 11:16 AM