Math is Figure-Out-Able!

#MathStratChat - September 10, 2025

Pam Harris, Kim Montague

In today’s MathStratChat, Pam and Kim discuss the MathStratChat problem shared on social media on September 10, 2025. 


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  0:02  
Hey, fellow mathers! Welcome to the podcast where Math is Figure-Out-Able, I'm Pam Harris.

Kim  0:09  
I'm Kim Montague. 

Pam  0:10  
Today you are. And this episode is a MathStratChat episode that's going to be kind of funny, where we chat about our math strategies. 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. Best part. Love it when you comment on each other's thinking.

Kim  0:27  
Yeah. So, this Wednesday, our math problem was. Which is larger? 5% of 15 or 10% of 30? How would you think about this problem? Pause the podcast. Solve it however you'd like. The problem is which is larger? 5% of 15 or 10% of 30?

Pam  0:45  
Dun dun dun. Alright, you go first.

Kim  0:48  
Okay, so it's a this or that. So, I am looking at the fact that 10% of 30, I just know is 3. 

Pam  0:58  
Okay. 

Kim  0:58  
And so then, once I know that, I recognize that 5% is half of 10% and 15 is half of 30, so I actually know that those are equivalent. So, I didn't really think. I never solved the 5% of 15. I just know it's... 

Pam  1:17  
Wait, wait,

Pam  1:18  
wait. How do you know they're equivalent?

Kim  1:22  
5% is half of 10%. 

Pam  1:24  
Okay.

Kim  1:26  
And 15 is half of 30.

Pam  1:29  
Yeah.

Kim  1:30  
So, I'm taking half the percentage and half the amount.

Pam  1:33  
Okay, alright, alright. But you also found 10% of 30. 

Kim  1:38  
I did (unclear).

Pam  1:39  
I'm going to find 10% of 15. 

Kim  1:42  
Okay. 

Pam  1:43  
So, 10% of 15 is 1.5. 

Pam  1:48  
So, that's where I'm getting myself confused. So, then 5% would be half of that. Which is 0.75. Somehow, that doesn't feel equivalent to me. What I do wrong?

Kim  2:04  
Or what I do wrong? 

Pam  2:05  
I don't know. 

Kim  2:06  
5% of

Kim  2:07  
15. 10% of 15. Oh! Look at me just diving in.

Kim  2:07  
Wow. 

Pam Harris  2:07  
So, help me out here.

Kim  2:16  
No, I'm wrong. Holy cow!

Kim  2:18  
Okay.

Kim  2:19  
Look at that!

Pam  2:19  
Is 10... 10% of 30 is 3, right? 

Kim  2:22  
Yes. 

Pam  2:22  
And 5% of 15. 10% of 15 is 1.5.

Kim  2:27  
Yeah. 

Pam  2:27  
And half of 10% is 5%, so half of 1.5 is 0.75. 

Kim  2:32  
I totally fell for it. Look at me. 

Pam  2:34  
Well, okay, so then help me make sense of the half and half thing. 

Kim  2:37  
What do you mean? 

Pam  2:38  
Well, when you said 10% (unclear).

Kim  2:40  
Because I'm taking less of a percent of a smaller number.

Pam  2:44  
Oh. Less of a percent of a smaller number is not going to be equivalent. So, half the percentage of a smaller thing by half is not going to be the same as...

Kim  3:04  
It's a fourth.

Pam  3:04  
...twice the percent. Oh, indeed, it is a fourth. That's a good relationship. You okay if we keep? 

Kim  3:07  
Yeah.

Pam  3:07  
You okay if we keep this (unclear).

Kim  3:07  
100%. 100%.

Pam  3:07  
Whew! Alright, you saw thinking live on chat. Here we go.

Kim  3:11  
Yeah, you think we do these problems ahead of time. Totally don't. (unclear). 

Pam  3:14  
Hey, you know,

Pam  3:15  
there was a response on LinkedIn a couple of weeks ago from Michael, and he said, "Oh, bam." And he shot out a really good strategy, except he made a slight error. 

Kim  3:24  
Yeah.

Pam  3:25  
In the first part. And it was kind of similar to this one.

Kim  3:27  
Mmhm. 

Pam  3:27  
Where it looked right, but it was just off. And, James, I think, is the one who said, "Take a second look." And I loved it because... 

Kim  3:35  
Loved that 

Pam  3:36  
...here's what James didn't do was say, "Dude, here's where you screwed up!" And told.

Kim  3:40  
Yeah. 

Pam  3:40  
He just said, "Take a second look." And then Michael said something like, "Never do math when you're tired publicly." 

Kim  3:45  
You know what, here we go. 

Pam  3:47  
James popped back and said, "No, it's the best time! It's the best way that we could learn!" And that they have great conversation. So, Kim, thanks for (unclear).

Kim  3:54  
Well, I think it's hilarious that you thought you were wrong and not me. (unclear).

Pam  3:58  
Well, I was like, "What is happening right now?!" I was trying to figure out

Pam  3:59  
what was going on. 

Kim  4:01  
Okay.

Pam  4:02  
Isn't 10% of 15, 1.5? Because if that's true, then we're... Okay.

Kim  4:06  
Alright, well, we can't wait to see what you do each week. Don't scream at me when you listen to this. "Kim, what's wrong with you?!" Join us on MathStratChat and let us know how you think about the problems. Comment on each other's strategies. Or post, "Kim's not thinking right."

Pam  4:24  
There you go. Or, I mean, I was like, "Okay, your logic kind of made sense, but I'm still trying

Pam  4:29  
to... What? 

Kim  4:29  
My kids would say, "Your brain's not braining today, Mom." 

Pam  4:29  
Oh, your brain's

Pam  4:31  
not braining. I like it. Alright, ya'll, we post the problems on Wednesday at 7:00 pm Central. When you answer, tag me and use the hashtag MathStratChat, then join us here to hear how we're thinking about the problem. We love having you as part of the Math is Figure-Out-Able movement. Math is Figure-Out-Able!