Total Cost 4E
Overview
Ms O’Sullivan buys 28 costumes at €5.30 each during a 15% sale.
Students identify the correct expression for the total (5.30 × 28),
compute it, decide whether to use 0.15 (discount amount) or 0.85 (final price factor),
subtract the discount, and round to the nearest euro.
Worked Example
Unit price = €5.30
Quantity = 28
Total before discount = 5.30 × 28 = €148.40
Discount rate = 15% = 0.15
Discount amount = €148.40 × 0.15 = €22.26
Price after discount = €148.40 − €22.26 = €126.14
Rounded to nearest euro = €126
Step Sequence
- Choose the correct operation to find the total: multiply price × quantity.
- Calculate the pre-discount total.
- Find the discount: multiply total by 0.15 (or use 0.85 as a one-step factor for the final price).
- Subtract the discount from the total to get the sale price.
- Round the final amount to the nearest euro.
Sample Prompts
- “Which expression gives the total cost before discount?”
- “To find the discount, would you multiply by 0.15 or 0.85?”
- “What is the price after subtracting the discount?”
- “Round your final price to the nearest euro.”
Why This Matters
Learners connect percentages to real purchases, building practical financial literacy and confidence using a calculator for multi-step money problems.
Prerequisite Knowledge Required
- Total Cost 4D – combining subtotals and totals (money addition).
- Percentages 3C – finding a percentage of an amount.
- Rounding 2B – rounding to the nearest euro.
Main Category
Arithmetic → Money → Percentages & Real-World Applications
Estimated Completion Time
Approx. 10–14 seconds per question.
40 questions total → Total time: 7–10 minutes.
Cognitive Load / Step Size
Each screen introduces one idea at a time (multiply → percentage → subtract → round), keeping working-memory load moderate and focused.
Language & Literacy Demand
Moderate. Short sentences with icon support (SALE badge, item table). Keywords (discount, total cost, after discount) highlighted in purple to anchor meaning.
Clarity & Design
- Neat price/quantity tables separate inputs from results.
- Consistent colour cues for operations and amounts.
- Clear SALE/percentage visuals to emphasise the discount step.
Curriculum Alignment (ROI Junior Cycle – Number)
- Calculate the cost of multiple items (multiplication of decimals).
- Find a percentage of an amount and interpret the result.
- Subtract to determine a discounted total; round appropriately.
Engagement & Motivation
A relatable school drama context frames a practical money-saving challenge, sustaining interest and purpose.
Error Opportunities & Misconceptions
- Confusing 0.15 (discount amount) with 0.85 (final-price factor).
- Forgetting to subtract the discount from the total.
- Decimal mistakes in multiplication or rounding.
- Applying the percentage to the unit price instead of the total.
Transferability / Real-World Anchoring
Highly transferable to shopping, budgeting, and evaluating sales. Encourages effective calculator use and estimation to sense-check results.
Conceptual vs Procedural Balance
Balanced. Concept (what a discount means) precedes procedure (how to compute it), reinforcing understanding and accuracy.
Learning Objectives Addressed
- Multiply to find a total cost for multiple identical items.
- Calculate a percentage of a total to find a discount.
- Subtract the discount to get a final price and round sensibly.
- Choose between 0.15 (discount) and 0.85 (net) factors appropriately.
What Your Score Says About You
- Less than 20: Building comfort with decimals and % steps — revisit 4D first.
- 21–29: Processes understood but % factor choice slips occasionally.
- 31–39: Strong calculation order — just check rounding and decimals.
- 40 / 40: Excellent financial fluency — ready for compound interest and profit/loss.