Grade
2
Same & Different: Unknown Number
Look at the two pictures. What do you notice?
![A. shows a number line that counts by 10s from 0 to 100. A green arrow goes from 100 to 20. The equation is red 100 minus blue 80 = green question mark. B. shows a number line that counts by 10s from 0 to 100. A green arrow goes from 80 to 100. The equation is blue 80 + green question mark = red 100.](/sites/default/files/inline-images/sPTwL7KtDu8lO1QrGovglVEPPo2GkfyHXUrAA1IDajNGqMq7EY.png)
- How are pictures A and B mathematically the same, and how are they different?
- A and B are the same because …
- A and B are different because …
- Make a third picture that represents a problem with a missing number. Explain how your picture is the same as pictures A and B, and how it is different.
Printable Version
Google doc for printing and copying
Reference for Educators
Sample problems and solutions