Cargo grids: name each change

Give each place an address

Two cargo grids let us compare matching places. Columns A and B run from left to right. Rows one and two run from top to bottom in this diagram. State that convention before using the addresses, because not every grid labels its rows in the same direction.

Check the upper-left cell

Start with cell A one in both grids. One circle becomes one diamond. The count stays at one, but the shape changes. Describe that specific feature instead of saying the whole grid changed. Small, checkable statements help another observer confirm what you found.

Count the crates

Now compare B one. There are two square crates before and three after. Three minus two is one, so one crate was added. Compare the same cell in both grids. Counting all shapes at once could hide which kind of object actually increased.

Follow the triangle

The triangle was in A two and is now in B two. Its old cell becomes empty while its new cell gains the triangle. That is one object moving, even though two cells change. The cargo has moved across the grid, not learned how to duplicate itself.

Pause: a different cargo move

Imagine a new pair of otherwise empty grids. A single square moves from A one to B two. Pause and answer two questions: how many objects moved, and how many cells changed? Explain what happened in both the old cell and the new cell before continuing.

Check both counts

One square moved, while two cells changed. A one lost the square and B two gained it. Neither answer is a trick: the questions count different things. Always name the unit of your count, such as objects, cells or added crates, instead of giving an unexplained number.

A move can leave two clues

Fun fact: one move can leave two visible clues. The old cell becomes empty and the new cell becomes occupied, even though only one object moved. That is why a before-and-after comparison needs a clear counting rule. The biggest number is not automatically the best description.

Describe, then count

Continue to the worksheet below. Compare the same cell in each grid, name shape and count changes, then trace the moved triangle. Count the objects in the final grid as a separate question. Use the pictures or their equivalent written descriptions to justify each answer.