Math is Figure-Out-Able with Pam Harris

#MathStratChat - March 13, 2024

March 13, 2024 Pam Harris
Math is Figure-Out-Able with Pam Harris
#MathStratChat - March 13, 2024
Show Notes Transcript

In today’s MathStratChat, Pam and Kim discuss the MathStratChat problem shared on social media on March 13, 2024. 

Note: It’s more fun if you try to solve the problem, share it on social media, comment on others strategies, before you listen to Pam and Kim’s strategies.

Check out #MathStratChat on your favorite social media site and join in the conversation.

Twitter: @PWHarris

Instagram: Pam Harris_math

Facebook: Pam Harris, author, mathematics education

Want more? Check out the archive of all of our #MathStratChat posts!

Pam  00:00

Hey, fellow mathematicians! Welcome to the short podcast where Math is Figure-Out-Able! I'm Pam.


Kim  00:06

And I'm Kim.


Pam  00:07

And this is a short episode because it's a MathStratChat episode, where we chat about our math strategies. Because every Wednesday evening, I throw out a math problem on social media, and people from around the world chat about the strategies they use, and comment on each other's thinking. 


Kim  00:22

Alright, so this week, our problem was 81 minus 54. We're wondering how you would solve this problem. Pause, give yourself time to think, and then come back to hear how we're going to solve it. 81 minus 54.


Pam  00:36

Okay, I'm going to go first today. 


Kim  00:37



Pam  00:38

So, I can think about 81 minus 54 as nine 9s. 


Kim  00:43



Pam  00:43

Subtract six 9s. But I'm going to choose not to.


Kim  00:49



Pam  00:50

I'm actually... As soon as I started thinking about nines I said to myself, "Oh!" Actually 81 is also three 27s. 


Kim  00:58

Oh, nice. Ooh, I like it.


Pam  01:00

And 54 is two 27s. So three 27s subtract two 27s, bam, is just one 27. And I am particularly smiling about that (unclear). 


Kim  01:11

Yeah, that's really nice. 


Pam  01:12

That makes me happy. 


Kim  01:12

I like, I like. 


Pam  01:13

Thanks. Thanks. Thanks. 


Kim  01:14

I did not think about that (unclear).


Pam  01:15

Which is also... 


Kim  01:16

Because the nines, (unclear).


Pam  01:17

Yeah. It's also the three 9s if I'd subtracted nine 9s minus six 9s. Yeah, 


Kim  01:21

Super nice.


Pam  01:22



Kim  01:22

I love it. I love it. I love it. Okay, I'm going to do... I'm going go 81 minus 54 is equivalent to 80 minus 53. So, I'm going to (unclear).


Pam  01:34

Oh, I hate that.


Kim  01:36

Why? You hate mine? You hate my thinking? 


Pam  01:38

Well, I...


Kim  01:40

Alright. So, 80 minus 53, I know is 27. Because... Why do I know that? (unclear).


Pam  01:48

Yeah, see. Why do you know that?


Kim  01:49

I know. Because I play I Have, You Need a lot. 


Pam  01:51

But do you play I Have, You Need with a total of 80? 


Kim  01:54

No, but because I've played with 100 and with 10, then that that informs every other multiple of 10 in the world for me. 


Pam  02:03

(unclear). I mean, so literally, you don't think like 80 minus 60 minus 7 more. Or 80 minus 50, and then pop back the 3. You don't do any of that? 


Kim  02:12



Pam  02:13

Yeah. So, I appreciate your constant difference strategy of thinking about 81 minus 54 as the equivalent 80 minus 53. If I was going to do constant difference, I would have shoved those both up 6 and turn that into 87 minus 60.


Kim  02:26

Also legal.


Pam  02:29

Which I think is just totally easier to think about than 80 minus 53. But to each his own. It's okay. 


Kim  02:34



Pam  02:35

It's all good. 


Kim  02:36

Maybe because I'm not writing anything down, and so shifting up 6, then the two numbers, I'd have to think about more than the shift of 1 down (unclear). 


Pam  02:44

Yeah, but. Totally. I get that. I get that. But 87 minus 60 is so much easier for me to think about than 80 minus 53.


Kim  02:51

Yeah. You know what's super cool is that when you have done some work with numeracy, and you have a variety of strategies, we're saying things like, "I prefer this one for these numbers," and "I like this one," but "Oh, I follow you on this one." Like, that's what we want, right? For adults. For kids. We want them to have so many different strategies, but it's always a choice. What do you want to do? (unclear).


Pam  03:12

(unclear). Exactly. You're empowered because you have choice. It's not choice if you've only got one thing. Especially you don't even understand that thing.


Kim  03:19

I know. I know. Alright, listeners. We want to know what your choice is. Will you share it with us? Take a picture of your work. Write something down, so we can see what you did. And tell everyone on social media. Invite others to join MathStratChat. Make sure you comment on other people's thinking.


Pam  03:34

And I love the fact that we have teachers. I'll shout out Adina the other day threw out a MathStratChat problem to her class and posted her classes strategies in their handwriting. That was fantastic! Please consider doing some of that. While you're there, tag me and use the hashtag MathStratChat. And check out our next MathStratChat problem that we post Wednesday evenings around 7pm Central Time, and then come back here to hear how we're thinking about the problem. 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!