{
  "version": 1,
  "kind": "barmodel",
  "title": "How many children come by bus?",
  "description": "A part-whole bar model: a class of 30 children, 12 who walk and the unknown rest who come by bus, with the whole braced over the bar.",
  "bars": [
    {"id": "class", "parts": [
      {"amount": 12, "text": "walk: 12"},
      {"amount": 18, "text": "bus: ?", "role": "emphasis"}
    ]}
  ],
  "braces": [{"over": ["class"], "amount": 30, "text": "30 children"}]
}