Session 09 — Banking and interest (concepts, not live rates as law)

Course: CALM (PED0770). Topic: CALM-RC-05. ~75 min.

Package: semester_ready\packages\CALM-RC-05\.

Not financial advice. Teaching rate is labelled. Connect to Math 30-3 percent and linear relations — do not modify the Math 10C/30-3 production courses; this is a cross-link in CALM only.

Official outcomes / topics

• CALM-R7: evaluate services and costs of financial institutions; EFT/ATM/online/telephone banking — benefits and limits.
• CALM-R4: financial goals — saving as a leftover allocation.
• Canon: accounts; institutions; interest; digital banking.
• Math link (CALM classroom): percent, simple interest I = Prt, compound as repeated percent; linear “y = starting + rate × time” as a sketch, not a diploma exam.

Learning targets

1. Contrast chequing vs saving purposes (access vs set-aside) without naming a real brand as “best.”
2. Compute simple interest on $400 at 3%/year for 6 months using I = Prt.
3. Contrast that with one-year compound once at 3% on $400.
4. Name two digital-banking benefits and two limits (fees, fraud, access).

Prerequisites

Session 08 leftover. Percent. Calculators.

Diagnostic / retrieval

3% of 400 = ? 12. Half year at simple interest = half of 12 = 6. If students say 3% of 400 is 3, repair place value.

Instruction

Not law: 3% is a 2026-08-18 teaching rate. Live credit-union rates change. Students must not copy this into a real application as a quote.

Simple interest: I = Prt with t in years. P=400, r=0.03, t=0.5 → I = 400 × 0.03 × 0.5 = 6. Amount A = 406.

Compound (once per year, 1 year): A = 400 × 1.03 = 412. Interest 12.

Two years annual compound: 400 × 1.03² = 400 × 1.0609 = 424.36.

Linear sketch (simple): A = 400 + 12t (t in years) — a line. Compound is not that line after year 1. Math 30-3 students may recognize percent and linear; we still do not assign their diploma items here.

Accounts: chequing = frequent EFT/ATM. Saving = less access, sometimes interest. Limits: ATM fees, holds, phishing. Online benefit: 02:00 transfer. Limit: no human help at 02:00; fraud risk.

Institutions: bank / credit union / caisse — evaluate using fees and access from a fictional fee table, not a sales pitch.

Fictional fee table (teaching): ATM other-network $2; e-transfer $0.50 or 0 (promo — still not a real offer); monthly chequing $4 if balance < $500.

Jordan leftover 478: if monthly fee $4, leftover 474. If they keep $500 in chequing to skip the fee, they cannot also spend that $500 — opportunity cost.

Timed visuals

id	trigger	duration	alt	teacher cue	tutor cue
CALM-VIS-09-PRT	After retrieval	70 s	I=Prt with 400, 0.03, 0.5	Units: t in years	Don’t pull live rates
CALM-VIS-09-LINE	Minute 28	60 s	Line A=400+12t vs dots 412, 424.36	“Compound leaves the line”	No crypto charts
CALM-VIS-09-FEE	Minute 48	40 s	$4 fee vs $500 minimum	Opportunity cost	No “open this account”

Modelling / worked examples

Work I = 400×0.03×0.5 on the board with place value. Then 400×1.03. Then 1.03².

Kiosk: $483 cash sitting in a jar vs saving account. Jar: $0 interest, theft risk. Account: teaching 3% simple on 483 for 1 month ≈ 483 × 0.03 × (1/12) ≈ 1.21 — small; the point is the method, not getting rich this month.

Guided practice + answers

1. Simple interest on $200 at 3% for 1 year: 6; A=206.
2. 6 months: 3; A=203.
3. Compound 1 year 3% on 200: 206 (same as simple when n=1 year once).
4. Why might ATM $2 × 8 uses = $16/month beat a “free” account that is far from town? Access vs fee — R7 evaluation.

Independent practice

• FOUNDATION: 3% of 400 and half of that.
• CORE: Full I=Prt for 400, 0.03, 0.5 and A.
• PROFICIENT: One-year compound vs two-year; compare to linear 400+12t at t=2 (424 linear vs 424.36 compound — close early, idea matters).
• ADVANCED: Fee scenario: 8 × $2 ATM = 16 vs $4 monthly + 2 ATM = 8; which is cheaper given this table; state this is not advice.

Project connection

Milestone 1: include one interest calculation on leftover or kiosk cash using 3% teaching rate, dated 2026-08-18.

Checks for understanding

“Is 3% the law in Alberta?” No. “Is compound always way bigger in 6 months?” Not in this 6-month simple vs 1-year compound mix — compare like terms.

Misconceptions

Wrong	Repair
“Interest is free money from the bank with no trade-off.”	Access limits; fees; inflation not fully taught today.
“The tutor will quote today’s RBC rate.”	Forbidden.
“Math 30-3 is this lesson.”	Cross-link only; don’t rewrite math course.
“I should screenshot my real account.”	Privacy: no.

AI Tutor prompts and safeguarding boundaries

Allowed: “Compute 400×0.03×0.5.” “Explain simple vs compound with these numbers.”

Forbidden: live rate fetch; product recommendation; asking for account numbers. Crisis → humans.

Human-tutor handoff

If a student is unbanked: fictional numbers only; no shame; counsellor/admin for real settlement help outside this lesson.

Exit ticket

I on $400 at 3% for 6 months? $6. One digital benefit and one limit. Dated: “3% teaching, 2026-08-18.”

Homework

Recompute for $250 at 3% for 1 year simple (7.50). No real bank visit required.

Teacher guidance

Do not import a bank guest speaker’s rate as PoS. Math 10C/Science 10 files are untouched. If a math teacher wants the link, they come here — we do not patch wrangler or math10c public.

Materials

Calculator; I=Prt card; fictional fee table; date stamp.

Preparation

Write “NOT A QUOTE” on the 3% poster.

Timing

Min	Move
0–8	3% of 400
8–24	Accounts + EFT benefits/limits
24–42	I=Prt and compound examples
42–58	Guided + independent
58–68	Fees / opportunity cost
68–75	Exit + date stamp

Online alternative

Calculator app. Teacher disables “search current rates” as a task.

Low-technology alternative

Pencil percent: 1% of 400=4; 3%=12; half=6.