homework in china for elementary students how tall is the table

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Homework In China – How Tall Is The Table?

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Posted September 24, 2018 By Presh Talwalkar. Read about me , or email me .

I adapted this problem from a similar one for elementary students, as tweeted by China Focus .

How tall is the table?

The problem is meant for children, but surely it will stump some adults. Can you figure it out? Watch the video for a solution.

"All will be well if you use your mind for your decisions, and mind only your decisions." Since 2007, I have devoted my life to sharing the joy of game theory and mathematics. MindYourDecisions now has over 1,000 free articles with no ads thanks to community support! Help out and get early access to posts with a pledge on Patreon .

(Pretty much all posts are transcribed quickly after I make the videos for them–please let me know if there are any typos/errors and I will correct them, thanks).

One way to solve the problem is algebra. We can make equations based on the height of objects. From the picture on the left we have:

cat + table – turtle = 170

From the equation on the right we have:

turtle + table – cat = 130

To solve for the table, we add these two equations, which then gives:

2(table) = 300

Then we can readily solve the height of the table is 150 cm.

I’m not sure if the students learned algebra yet, so I wanted to derive another method as well.

There is a neat way to solve the problem visually, by stacking the diagrams.

The height from the top of the cat at the bottom to the top of the cat at the top is 300. This is exactly twice the height of a table, as can be seen by removing irrelevant elements in the diagram, and shifting down by the height of the cat:

Thus the height of the table is half of 300, or 150.

China Focus tweet https://twitter.com/China__Focus/status/1039338689187332096

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Presh talwalkar.

I run the MindYourDecisions channel on YouTube , which has over 1 million subscribers and 200 million views. I am also the author of The Joy of Game Theory: An Introduction to Strategic Thinking , and several other books which are available on Amazon .

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One thought on “Homework In China – How Tall Is The Table?”

I did it visually as well but slightly different.

I noticed that in the the first picture 170 is higher than the table by the cat-turtle height and in the second the it is lower by the same amount. So the table height must be in the middle between 170 and 130, aka 150.

Comments are closed.

Chinese Word Problem: The Turtle, the Cat and the Table

Originally posted in English by China Focus on Twitter, this challenging math problem appeared on elementary school curriculum in China in 2018, and this image was adapted by Presh Talwalkar for mindyourdecisions.com. 

The problem looks simple enough at first glance—however, without knowing the heights of each animal, most students aren’t sure where to begin. Because this problem relies on one’s ability to understand spatial realities and manipulate them mathematically, it has stumped both young learners and adults alike. Here are a couple ways to approach it: 

Method 1: Algebraically  

For those students who have begun working with algebra, we can begin by assigning abstract variables to each object and constructing equations for each diagram: 

Table + Cat − Turtle = 170 cm  

Table + Turtle − Cat = 130 cm  

If we then add both equations together, we’ll get something like this: 

Table + Table + Cat − Cat + Turtle − Turtle = 300 cm  

Because both cats and both turtles will cancel each other out, we can then simplify to obtain the following: 

Table + Table (+ Cat − Cat) (+ Turtle − Turtle) = 300 cm  

Table + Table +  Cat  −  Cat  +  Turtle  −  Turtle  = 300 cm  

Table + Table = 300 cm  

At this point, we can conclude that if two tables would be 300 cm high, then one table would be 150 cm high! 

Method 2: Visually  

This method may be more accessible for students who have not begun algebra, or for whom visual methods come more easily than computational ones. Presh Talwalkar has designed a helpful image for this method, in which we stack both images atop each other: 

In this method, we can easily see that the height from the top of the head of one cat to the next cat is 300 cm. From here, we can subtract the cat from the equation and slide the measurement downwards by the height of one cat, effectively removing all the animals from the equation (similar to how we achieved this algebraically): 

At this point, we can conclude that the height of two tables is 300 cm, and therefore one table would be 150 cm! 

Many students (rightfully) approach math and word problems by looking for numbers to manipulate, deducing which operation(s) should be used, and finally crunching the numbers to achieve the final solution. However, many of the most challenging math problems contain few numbers to manipulate, and rely upon logic and higher reasoning to fill in the missing pieces and solve successfully. By equipping students with multiple methods of approaching and solving problems, as well as moving away from specific numbers and looking at problems more abstractly and strategically, good tutors and teachers can ensure young learners are prepared for anything their textbooks (or the world at large) will toss their way! 

This article was written by one of Aspire Learning Academy’s very own instructor, Daniel Marcotte.

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