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.
  1. 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 …
  2. 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