Same & Different: At the Beach

Emerson measured the mass of stones and shells they collected at the beach.
What do you notice?

A: A scale with 5 small stones shows 200 grams. B: A scale with 5 shells shows 200 grams.
  1. How are pictures A and B the same mathematically, and how are they different?
    • A and B are the same because …
    • A and B are different because …
  2. Make a third picture that shows objects on a scale. Explain how your picture is the same as pictures A and B, and how it is different.