Here is half of a simple house, drawn right beside a straight line. Imagine a mirror standing up on that line. What would the missing half of the house look like in the mirror? Would the door move? Would the roof slope the other way?

Four shapes sit beside a mirror line, each with its reflection already drawn. Watch how far every shaded square sits from the line, then check that its match lands the same distance on the other side.

Today we work this together on the board: a few squares are shaded on one side of the mirror line. We will shade the matching squares on the other side, counting how far each one sits from the line before we place its partner. When we finish the first picture, we will clear the board and try one fresh pattern with a new volunteer.

Today we work through these reflections together: first a 3-square picture, then a 5-square one, then a picture that touches the mirror line. Last of all, we reflect across a horizontal mirror line. A horizontal line lies flat across the page instead of standing up, so this time we count the squares up and down from the line rather than left and right.

What we learned

• A picture and its reflection match exactly across a mirror line.
• Each shaded square has a partner the same number of squares from the line.
• Always count back to the mirror line, not to the edge of the grid.

Coming up

Next we will reflect a whole shape across a line, so the shape flips over and faces the opposite way.