Spot the Changed Reading
Exactly one of these readings comes out different. Which one?
This engine’s own main skill is What Stays the Same When a Shape Moves. It practises identify a shape property alongside it.
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.