Exactly one of these readings comes out different. Which one?
The programme is “Slide 4 right”, then “Slide 2 right”, then “Flip in the line x = 4”. Every move on that list picks the outline up and puts it down without changing its size or shape, so the lengths of the sides, the angles at the corners and the area inside are all exactly what they were. What a rigid motion does change is WHERE things are, and here that is the coordinates of corner A. There is one more thing a flip changes and a slide or a turn never does: the letters ran anticlockwise round the outline and now run clockwise. The exam-safe habit is to sort every reading into "about the shape itself" or "about where the shape is": the first kind always survives, the second kind is the only place an answer can hide.
Step 1. Watch it move. Play the cards and watch the readings.
Step 2. The odd one out. Which single reading came out different?
What to say if they get stuck
Tap a reading and it is drawn twice: once on the faint outline where the shape started, once on the solid one where it is now. Scrub slowly and watch whether the two marks stay the same.
A slide, a turn and a flip all pick the outline up without stretching or squashing it, so every length, every angle and the area come through untouched.
A flip is the only one of the three that reverses the outline, and this programme has one of them, so the letters end up reading round the other way.
How preserve measure under a rigid transformation differs from the skills beside it
The same exercise practises several skills, and telling them apart is often the difficulty rather than the exercise itself. On this page the skill is: use the fact that translation, rotation, and reflection preserve lengths and angles, and it stops where excludes calculating an unknown measure from unrelated angle or length rules.
Questions parents ask about preserve measure under a rigid transformation
Answered from what the skill map records about this skill, not from a template. Every answer here is on the page, and the same questions are the page's FAQ structured data.
Use the fact that translation, rotation, and reflection preserve lengths and angles. It is one of 55 named maths skills in the 11+, in the geometry strand, and this page carries 1 interactive exercise that practises it.
Only an enlargement changes lengths - and none of these moves is an enlargement. The wrong answers on this skill are built out of that, not out of random numbers, so it is worth naming out loud before your child meets it under time pressure.
Point at the next move rather than explaining the whole rule. Reflections, rotations and translations only change where a shape sits, so read the measurement straight off the original figure.
The skill map draws the line here: Excludes calculating an unknown measure from unrelated angle or length rules. A question past that line is testing a different named maths skill, which is worth knowing before you spend a week practising the wrong one.
The geometry strand holds 15 skills that are tested together, and the pages next to preserve measure under a rigid transformation are reflect a coordinate, reflect a shape and rotate a coordinate. Each has its own exercise and its own link, and none of them needs an account.
Use Spot the Changed Reading, embedded on this page. It is the exercise the skill map attaches to preserve measure under a rigid transformation, it runs in the browser with no account to make, nothing is scored, and nothing a child does here is recorded or sent anywhere. It also has its own link, so you can send it to a child without sending them anywhere else first.
Knowing which maths topic to practise is most of the work
A free diagnostic covers arithmetic, fractions, geometry, measure and data handling, and comes back with the topics to spend the next few weeks on.
