A mine site office desk mid-decision: pit map, labour roster, equipment quote, water chart and a budget that cannot fund everything
Year 7 · Unit 02 · Lesson 03

Opportunity Cost at the Mine Gate

One idea must land: opportunity cost is the value of the NEXT-BEST alternative — singular — and it exists because wants outrun resources.

Last lesson ended with one budget and three things screaming for it. Today the scream gets a name. Students take the General Manager’s chair at a desk with three folders and $3,550,000 — engineered so the two “future” options fit the budget to the exact dollar, and every possible path still buries something of value. That buried thing is the lesson.

Spark

The Saturday trap

Harvest a few Lesson 2 exit seeds aloud — “you already made this decision; today it gets a name.” Then the trap: Saturday morning — sleep-in, footy, or a $60 shift; they chose footy. What did it cost? Answers lock, then the reveal: not “nothing,” and not everything added up — the single next-best alternative.

Say it once, cleanly: “Opportunity cost is what the best road you didn’t take was worth.” The trap exists to kill the everything-summed misconception before it settles.
Core

Read like an analyst

The Jindarra briefing lands with a three-mark protocol: BOX the limited resource, UNDERLINE the competing options, CIRCLE the sentence that proves choosing is unavoidable. Fast check: the box belongs on $3,550,000 — anyone boxing a folder hasn’t found the scarcity yet.

The recovery question for a misplaced box: “which number makes all the other numbers fight?”
Workshop

The decision matrix + the discussion

Maths before arguing: the matrix reveals A+C fits with change, B+C lands on the budget to the dollar, A+B is impossible. Then the structured discussion — pair, square, room: “is exploration a luxury or a survival move?” — where Unit 1’s non-renewable truth resurfaces as admissible evidence. Every GM then commits: allocation chosen, next-best named precisely, and the fork sketched with the abandoned arm labelled.

The perfect-fit path is the sharpest teacher: B+C spends every dollar and still buries option A. Fitting the budget ≠ free.
Land it

Exit ticket + the flow seed

Definition with “next-best” mandatory; the descriptor in their own words — why does opportunity cost exist at all? — and the Lesson 4 seed: follow the wages into town and ask whether the money ever comes back. The loop they can’t quite close IS the circular flow. Next lesson closes it.

Teacher intel

Which number makes all the other numbers fight? (The budget — scarcity’s home address.)
You chose B+C and it fits perfectly — so was your decision free?
If the budget doubled, would opportunity cost disappear? (The wants queue past the window.)
What was the opportunity cost of your phone time last night?
Watch for“Opportunity cost = everything given up, summed” (next-best only) · “free things cost nothing” (time is a resource) · “the cost is the money spent” (the cost is what else that money could have done).
Running shortPairs-only discussion, skip the fork sketch. Protect the Saturday trap, the highlighting, one completed matrix, and the Lesson 4 seed.
SupportMatrix totals pre-filled — judge the fits and name the foregone option only. The highlighting protocol scaffolds itself.
ExtendDeal the fourth folder: return $1,000,000 to the owners. A new option can move your next-best — opportunity cost shifts when the menu does.