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Translation

Slide a shape using a column vector, read the vector from a diagram, and find missing values.

In the exam for Cambridge IGCSE Maths 0580, Edexcel IGCSE Maths 4MA1, Cambridge O Level Maths 4024 · 42 real past-paper questions below

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What a Translation Does

A translation slides a shape. It does not turn, flip or change size. A column vector says how far it slides.

Formula

NumberMeaning
Topacross: plus is right, minus is left
Bottomup or down: plus is up, minus is down

Key idea

So this vector means 3 right and 2 down. Every corner moves exactly the same way.

Translating a Shape by a Vector

The most common question, 1 mark: translate a triangle by . Move every corner, then join them.

Worked example

  1. 1

    — Top number: −4 means 4 left. Bottom number: 3 means 3 up. Every corner makes this same move.

  2. 2

    — Add the top number to the corner's x-coordinate. Adding −4 moves 4 left.

  3. 3

    — Add the bottom number to the same corner's y-coordinate. Adding 3 moves 3 up.

  4. 4

    — Write the new x and y together as the image of this corner.

  5. 5

    — Second corner, same move: add −4 to x and 3 to y.

  6. 6

    — Work out each bracket: 4 − 4 = 0 and −1 + 3 = 2.

  7. 7

    — Third corner, same move: add −4 to x and 3 to y.

  8. 8

    — Work out each bracket: 2 − 4 = −2 and 1 + 3 = 4.

  9. 9

    — Join the three image points. The image is the same size and faces the same way as the object.

Common mistake

Using the top number to move up. The top number is across, the bottom is up or down.

Reading the Vector From a Diagram

When both shapes are drawn, pick one corner and the same corner on the image. Count across, then up or down.

Worked example

  1. 1

    — Pick one corner of the object and the same corner on the image.

  2. 2

    — Across is image x minus object x. Taking away −1 adds 1, so the move is 5 to the right.

  3. 3

    — Up or down is image y minus object y. A negative answer means down, so 2 down.

  4. 4

    — Write the across number on top and the up or down number underneath.

  5. 5

    — Check: add the vector to the object corner. It lands on the image corner.

Common mistake

Matching a corner to a different corner of the image. Use the same corner on both shapes.

Finding Missing Values

The 3-mark question: a point or a vector has letters in it. Work one row at a time: across first, then up or down.

Worked example

  1. 1

    — The object point has a letter for x. The vector has a letter on the bottom. The image point is known.

  2. 2

    — Across row: object x plus the top number equals image x.

  3. 3

    — Take 3 from both sides to get d on its own.

  4. 4

    — Up or down row: object y plus the bottom number equals image y.

  5. 5

    — Take 2 from both sides. −4 − 2 = −6, so the move is 6 down.

  6. 6

    — Check: move (4, 2) by the vector (3, −6). It lands on the image point.

Common mistake

Working out object minus image. That gives the vector backwards, with every sign wrong.

Key idea

Write one equation for each row. Most of the marks are for the working, so an answer found by guessing scores about 1 mark.

Which Method? Read the Question

Look at what is given and what is missing.

You seeYou do
Translate by a vectortop: across, bottom: up or down
Two shapes, find the vectorimage minus object
Letters in a point or vectorone row at a time
Describe fullyDescribing Transformations
Image flipped or turnedReflection or Rotation

Key idea

A translation never changes the way a shape faces. If it looks turned, it is not a translation.

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Real past-paper questions on translation

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