Hey, fellow mathematicians! Welcome to the podcast where Math is Figure-Out-Able! I'm Pam Harris.
And I'm Kim Montague.
And this episode is a MathStratChat episode. MathStratChat is where every Wednesday I throw out a math problem on Twitter, Facebook, and Instagram, and people from all around the world chat about the strategies they use. We love seeing everyone's thinking. [music continues on]
[Pam and Kim laugh].
(unclear).
Oh, gosh. Okay. [Kim laughs].
And now, you can't talk. I love it. Do you want me to do your part?
No.
Hey, This Wednesday our math problem was eleven-twentieths minus two-fifths. How would you solve this problem? Pause the podcast, solve the problem any way you want. The problem is... I already forgot what it is. What is it? Eleven-twentieths minus two-fifths. Solve it, then come back to hear how we solved it. And go.
I'm a mess. Okay. Do you want to go first or do you want me to?
I don't even remember who's. I think I'm going to go first. I'm going to go first.
Okay, sounds good.
I think it's my turn. Eleven-twentieths minus Okay.
Alright, I'm listening. two-fifths. It's just screaming nickels to me. Okay, so 11 nickels out of 20 nickels, subtract. Now, I have to think about two-fifths in terms of money. A fifth to me is $0.20, so two-fifths is $0.40. So, I'm thinking about how many nickels are in $0.40. So, I'm thinking about 8 nickels in $0.40. So, I've got eleven-twentieths or 11 nickels, subtract eight-twentieths or 8 nickels. So, 11 nickels, minus 8 nickels,
is 3 nickels. So, that's 3 nickels out of the 20 nickels in $1.00, three-twentieths. I have a question. When you just said 11 nickels minus 8 nickels. Is that what you said?
Mmhmm.
Did you think about what 11 nickels, like the value of that, and the eight nickels? Or did you not consider the value until you got done?
I totally thought about just 11 minus 8 being 3.
Oh, interesting.
But not you? You were thinking about?
Yeah. I didn't hear you say, "11 nickels, which is this much," and so...
Eleven nickels would be like $0.55.
Yeah.
Subtract.
I just didn't know if you thought about that along the way too. Interesting.
Well, the two-fifths I thought about as $0.40.
Yeah.
So, that's... I can't see my own writing now. $0.55 minus $0.40 is $0.15. So, that would be a way to get the 3 out of 20.
Yeah.
I did not do that at all. No.
Oh, that's interesting. Okay.
What were you thinking?
Alright, so I did not think about nickels. I think the reason that I asked you that question is because the same numbers would have popped up for me had they been for you, if you would have considered the value because I thought percents. And so, I thought about eleven-twentieths as 55%. Which I know because ten-twentieths is 50%, and then it's just 5% more. So, that's 55%. And then, two-fifths, I just know the fifth. And so, that's 40%. So, I wrote down on my paper 55% minus
40%, which is 15%. And that's three nickels. And so, when you didn't say the 55 and 40, I just found that interesting.
Yeah. And so, how do you know that? When you said 3 nickels, what's that fraction?
Fifteen percent is fifteen-hundredths, and that's the same as three-twentieths.
Nice. Super, I like it.
Alright, we cannot wait to see your math strategy, listeners. I wonder if it was like one of ours or something completely different. Represent your thinking, take a picture of your work or screenshot your phone, and tell the world on social media. And while you're there, check out what other people did, and comment on their thinking.
Yeah, and tag me on Twitter at @PWHarris. Or Instagram, PamHarris_math. And Facebook, Pam Harris, author, mathematics education. Why didn't we use the same thing everywhere? We don't know. But make sure that you use the hashtag MathStratChat. And make sure you check out the MathStratChat problem we post
00 p.m. Central Time, and pop back here to hear how we're thinking about the problem. Because we love having you as part of the Math is Figure-Out-Able movement. Let's keep spreading the word that Math is Figure-Out-Able!