Grade
2

Same & Different: Which Number Is Missing?

Look at the two pictures. What do you notice?

A: A number line shows jumping by 10s back from 145 to 85. Red 145 minus green 60 equals blue question mark. B: A number line shows jumping by 20s from 60 to 120, then jumping by 10s to 140, then jumping by five to 145. Green 60 + blue question mark = red 145.
  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. Think of an equation using 60, 85, and 145. Choose one number for the unknown. Make a third picture to represent your equation. Explain how your picture is the same as pictures A and B, and how it is different.
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Reference for Educators

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