Pam  0:00  
Hey, fellow mathers! Welcome to the podcast where Math is Figure-Out-Able. I'm Pam.

Kim  0:06  
And I'm Kim.

Pam  0:07  
And this episode is a MathStratChat episode where we chat about our math strategies for super cool math problems. Every Wednesday evening, I'll throw out one of those super cool math problems on social media. People from around the world chat about the strategies they use and comment on each other's thinking.

Kim  0:23  
Okay, so this week, our math problem was if 21 is seven-tenths of a number, what is nine-tenths of that number? If 21 is seven-tenths of a number, what is nine-tenths of that number? 

Pam  0:37  
Dun, dun, dun. 

Pam  0:37  
Alright 

Kim  0:39  
(unclear) yourself and then come listen.

Pam  0:41  
Yeah. Do you need... Are you writing stuff down for these last few problems?

Kim  0:47  
I'm writing just enough for me. It's totally chicken

Kim  0:50  
scratch.

Pam  0:50  
Me too. I'm really chicken scratch for this one. 

Kim  0:53  
Yeah.

Pam  0:54  
You go first.

Kim  0:55  
Okay, so if 21 is seven-tenths of a number, then I'm thinking that I want to think about I want to scale down, and I want to scale to find out what one-tenth is. 

Pam  1:09  
Okay.

Kim  1:09  
So, I'm going to divide both by 7. So, seven-tenths divided by 7 is one-tenth.

Pam  1:15  
Mmhm. 

Kim  1:15  
And then 21 divided by 7 is 3. So, then I can just scale back up for nine-tenths.

Pam  1:22  
Because

Pam  1:22  
you need 9 of those one-tenths. (unclear). 

Kim  1:24  
Yeah, so that would be 27.

Pam  1:26  
Okay, cool. So, I'm going to do... I'm going to start the same way thinking about if I've got seven-tenths, I only want one-tenth, so divide by 7. And get 3 is one-tenth of the number. And instead of scaling it up times 9, I'm going to say I've got that one-tenth is 3. And I knew... So, then I would know three-tenths is times 3. So, that's 9. 

Kim  1:51  
Mmhm.

Pam  1:52  
And seven-tenths was 21. And three-tenths is 9. So, 21 and 9 means the whole number is 30.

Kim  2:00  
Mmhm.

Pam  2:00  
And nine-tenths of 30 would be one-tenth less. Wow, that was really convoluted. Can you... I'm going to do it that way. Nine-tenths of 30 is one-tenth less. We already knew one-tenth was 3, so 30 minus 3 is 27.

Kim  2:14  
Yeah.

Pam  2:14  
When I got to that point where it was we knew that the number was 30, and we're looking for nine-tenths of 30. Do you have a better strategy for nine-tenths of 30 than to take one-tenth away?

Kim  2:26  
You know what I thought you were going to do was when you figured out that one-tenth was 3, and then you said something about 3. I thought you were factoring the 9 into 3 and 3. So, like nine-tenths being...

Pam  2:39  
Three-tenths, 3 times. 

Kim  2:40  
Mmhm. 

Pam  2:41  
Ah.

Kim  2:41  
Yeah,

Kim  2:41  
so then I thought you were going to go three-tenths would be 9, so then scale that by 3 to get nine-tenths

Kim  2:48  
for 27. 

Pam  2:49  
Yeah, cool. I like it. 

Kim  2:51  
Wait. Can

Kim  2:52  
I say though that I like that you did Over here because on my paper, when I wrote, I had 21 and seven-tenths kind of in a ratio table. 

Pam  3:01  
Oh.

Kim  3:01  
And when you did divide by 7, kind of start the way I did, then you had 3 times one-tenth. Then you said 30 is ten-tenths. Then you already had in your ratio table, back up that one-tenth. They were like right next to

Kim  3:18  
each other the way I wrote it.

Pam  3:26  
Oh, the entries were all there. The ten-tenths and the one-tenth were there. (unclear)

Kim  3:27  
Yeah, yeah. 

Pam  3:27  
Yeah, nice. 

Kim  3:27  
Alright.

Pam  3:27  
I did not. I had chicken scratch all over the place. Nobody could have found those on my paper. 

Kim  3:28  
Mine was very useful.

Pam  3:28  
With that system, then yeah, that model can be very helpful to keep track of stuff that you might be able to use further in the problem.

Kim  3:34  
Yeah, yeah. Alright, well, we can't wait every week to hear what you do. Join us on MathStratChat and let us know how you think about the problems. And the most fun is when you comment on each other's strategies.

Pam  3:45  
We love it when you do that. Ya'll, we post the problems on Wednesdays around 7:00 p.m. Central. When you answer, tag me and use the hashtag MathStratChat. Then join us to hear how we're thinking about the problem. Ya'll, we love having you as part of the Math is Figure-Out-Able movement. Math is Figure-Out-Able!