Consumer Math
Consumer math transforms abstract percentages into tangible life skills when students calculate whether that 40% discount on a $800 laptop truly saves money. These calculations appear in every shopping decision, loan application, and budget planning session your students will encounter.
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Why it matters
Consumer math skills directly impact financial well-being throughout life. A student who masters unit price comparisons saves $1,200 annually on groceries by choosing better deals. Understanding simple interest prevents costly mistakes—borrowing $50,000 at 6% for 4 years costs $12,000 in interest alone. VAT calculations become essential when students travel internationally or start businesses. The LK20.10.finance curriculum emphasizes these practical applications because Norwegian students need to navigate 25% VAT rates and compare prices across multiple retailers daily. Students who grasp discount calculations avoid impulse purchases during sales events, while those comfortable with markup percentages make informed decisions about extended warranties and service fees that can add 20-30% to purchase prices.
How to solve consumer math
Consumer Maths
- Percent of: multiply the amount by the percent as a decimal (20% of 50 = 0.20 · 50).
- Discount: new price = original × (1 − discount%).
- Markup / tax: new price = original × (1 + rate%).
- Simple interest: I = P · r · t, where P is principal, r is yearly rate, t is years.
Example: An $80 jacket is 25% off: new price = 80 × 0.75 = $60.
Worked examples
A jacket costs $600.00. It is 30% off. What is the sale price?
Answer: 420
- Calculate the discount amount → 30% x 600 = 180 — 30% of $600.00 is $180.00.
- Subtract the discount from the original price → 600 - 180 = 420 — Sale price = original price minus discount = $420.00.
A smartwatch costs $4,000.00 before VAT. Norwegian VAT is 25%. What is the total price?
Answer: 5000
- Calculate the VAT amount → 25% x 4000 = 1000 — VAT = 25% of $4,000.00 = $1,000.00.
- Add VAT to the price before tax → 4000 + 1000 = 5000 — Total price including VAT is $5,000.00.
Shop A sells 6 yogurts for $130.00. Shop B sells 1 for $25.00. Which shop has the better deal?
Answer: Shop A
- Calculate Shop A unit price → 130 / 6 = 21.67 — Shop A: $130.00 divided by 6 = $21.67 per item.
- Compare unit prices → 21.67 < 25 — Shop A's unit price ($21.67) is lower than Shop B ($25.00), so Shop A is the better deal.
Common mistakes
- ✗Students calculate 30% of $600 as $30 instead of $180, forgetting to convert the percentage to decimal form (0.30)
- ✗When finding sale prices, students subtract the percentage directly: $800 - 25% = $775 instead of calculating $800 × 0.75 = $600
- ✗For VAT problems, students add the percentage as dollars: $4000 + 25% = $4025 instead of $4000 × 1.25 = $5000
- ✗In unit price comparisons, students compare total prices rather than dividing: choosing $130 for 6 items over $25 for 1 item without calculating per-unit costs
Practice on your own
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