Cardinality — the last number said names the total count (CCSS K.CC.B.4)
Exercise Difficulty 3 ~1 min math.gK.f.ns.cardinality.ex_02

Reorder Invariance

Prompt

Here is a picture of 7 stars. I will rearrange them. How many are there now?

M-K-F-EX-10-A Illustration
Two-panel illustration: (left panel) 7 yellow 5-pointed stars in a horizontal line, evenly spaced on a navy-blue backgro

Two-panel illustration: (left panel) 7 yellow 5-pointed stars in a horizontal line, evenly spaced on a navy-blue background; (right panel) the same 7 stars arranged in a circle around a small smiley moon, on the same background. A curved arrow labeled 'I REARRANGED THEM' connects the panels.

How it's presented
mode two picture sequence
picture a
7_stars_in_a_line
picture b
7_stars_in_a_circle
Answer criteria
type cardinal answer
rubric
States '7' for picture B without recounting; if recount, accept '7' as practicing.
expected
7
Hints
  1. Did any stars disappear?
  2. If the number of things hasn't changed, has the COUNT changed?
Misconceptions to watch
  • Recounts picture B and accepts a different answer (no order-irrelevance).
  • Thinks rearranged stars are a 'different' set.
Used in lessons