Friday
Friday: Grids All Around
Rocket spreads a hand-drawn map of the yard on the Blueprint Table. "Shed at (2, 5). Gate at (2, -3). Same x!"
"So the path between them is straight up and down," Raven says. "And eight squares long. What do you notice?"
"Five minus negative three is eight," Rocket says. "Across zero again."
Nova hovers over the map. "Where else do you see grids?" she asks.
"Game boards," Raven says. "Seat charts. Street maps with letters and numbers."
"Spreadsheets," Rocket adds. "Columns across, rows down. A cell is a coordinate."
Nova hums. "Next week you unfold a box," she says. "Every face gets a place on the grid too."
Everyday grids
| Where | The coordinates | What a shared coordinate means |
|---|---|---|
| A yard map | squares across and up from a corner | two places on one straight path |
| A game board | a column letter and a row number | two pieces in the same column or row |
| A seating chart | row and seat | two seats side by side in one row |
| A spreadsheet | a column and a row make a cell | two cells in one column stack up |
| The floor grid | (x, y) in squares from the origin | a wall you can measure by subtracting |
A grid is any place where two numbers name a spot. Whenever two spots share one number, the line between them is straight.
And a straight line on a grid is a subtraction: the two numbers that differ, taken apart.
How to work with any grid polygon
- Plot the vertices and join them in order. Count the sides: one per vertex.
- For each side, find the shared coordinate. Subtract the other two coordinates for the length.
- Add the sides for the perimeter. Cut the shape into rectangles and triangles for the area.
- Name the quadrant of each vertex: I upper right, II upper left, III lower left, IV lower right.
- Read the question.
- Tap your answer.
Point P is at (-3, -2). Which quadrant is it in?
A game board has corners (-2, -2), (3, -2), (3, 3), (-2, 3). What is its perimeter in squares?- Read the question.
- Tap your answer.
A game board has corners (-2, -2), (3, -2), (3, 3), (-2, 3). What is its area in square units?| Week review | True or false? |
|---|---|
| Coordinates are written (x, y): across first, then up. | ? |
| Points with the same y-coordinate make a vertical side. | ? |
| The length from (-3, 2) to (4, 2) is 7. | ? |
| Quadrant III is the upper left, where x is negative and y is positive. | ? |
| Perimeter is the sum of all the side lengths. | ? |
- ?We named every corner of the main room with coordinates and found the walls by subtracting.
- ?We found perimeter and area, and crossed zero into all four quadrants.
- ?We ran Build Lab and checked string walls against the tape measure.
- ?We laid out the whole clubhouse outline from Raven's wall table and caught Rocket's slip.
Count the squares between them, then write the two coordinates and subtract. Do they agree?
A week of corners and coordinates. Tomorrow is Build Day: tape a grid with your family and string a shape.