Reflection in a mirror line: what children learn
Year 5 pupils identify, describe and represent the position of a shape following a reflection or translation, using the appropriate language, and know that the shape has not changed.
In this game children reflect points in vertical and horizontal mirror lines on a coordinate grid. The reflected point is the same distance from the mirror line as the original, on the other side.
This topic covers the Year 5 statutory requirement in the National Curriculum in England (Geometry – position and direction): pupils should be taught to “identify, describe and represent the position of a shape following a reflection or translation, using the appropriate language, and know that the shape has not changed”. Year 5 pupils are usually aged 9–10.
There is no direct equivalent in the US Common Core State Standards. Reflections on a grid are Grade 8 in Common Core (8.G.A.1); line symmetry is 4.G.A.3.
How to play
Answer 10 questions before the clock runs out. Tap an answer, or press 1 to 4. Each game has 10 multiple-choice questions and a 150-second timer. A wrong answer shows the correct one before moving on. You earn up to three stars depending on your score.
Step by step
- Find the mirror line. A vertical mirror line goes up and down. A horizontal one goes across.
- Measure the distance. Count how many squares the point is from the mirror line.
- Go the same distance the other side. The reflection is the same number of squares away, on the opposite side.
- Only one number changes. A vertical mirror line changes the x-coordinate. A horizontal one changes the y-coordinate.
Worked examples
Example 1: Reflect (2, 3) in the vertical line through 5 on the x-axis.
Working: 2 is 3 squares from 5, so go 3 squares past 5: 8.
Answer: (8, 3)
Example 2: Reflect (4, 1) in the horizontal line through 3 on the y-axis.
Working: 1 is 2 squares below 3, so go 2 squares above: 5.
Answer: (4, 5)
Example 3: Reflect (5, 2) in the vertical line through 5 on the x-axis.
Working: The point is on the mirror line.
Answer: (5, 2)
Common mistakes and how to fix them
- Changing both coordinates. Only the coordinate across the mirror line changes.
- Counting the distance from the axis, not the mirror line. Count from the mirror line every time.
- Putting the reflection on the same side. A reflection always flips to the other side of the mirror line.
Activities to try at home
- Use a small mirror to reflect drawings and letters.
- Fold paper with a blob of paint to make a symmetrical picture.
- Draw half a shape on squared paper and reflect it.
Ideas for the classroom
- Pupils reflect shapes on squared paper and check with a mirror.
- Give a shape and its reflection and ask pupils to draw the mirror line.
- Compare reflections and translations of the same shape.
Free printable game and worksheet
The free printable starts with a game sheet, such as a colour-by-answer picture, an answer maze or a secret-code joke, followed by a worksheet. Both use the same checked questions as the online game, and the answers are on the last page. Print it, or save it as a PDF from your browser’s print menu.
Open the free printable game and worksheet
Frequently asked questions
Does a reflected shape change size?
No. A reflection flips the shape, but it stays the same size and shape.
What comes next?
In Year 6, pupils reflect shapes in the axes on a grid with four quadrants.
Can it be played with a keyboard?
Yes. Press 1, 2, 3 or 4 to choose an answer.