Lesson Notes By Weeks and Term v3 - Junior Secondary 2
Transactions in the homes and offices
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Subject: General Mathematics
Class: Junior Secondary 2
Term: 1st Term
Week: 10
Theme: Basic Operations
This page supports the lesson note with a companion video and a short classroom-ready summary.
For class groups and homework, share this lesson page so learners also get the summary, objectives, and full lesson context.
Students should be able to: Solve problems relating to of fice and household arithmetic Solve simple commercial arithmetic relating to profit, in terest, discount and commission.
This section provides a detailed breakdown of the core concepts, definitions, formulas, and worked examples relevant to the topic. These questions are designed for immediate classroom practice under teacher supervision.
Question: Mr. Aliyu's transport company bought fuel worth N45,000, paid driver's wages of N25,000, and spent N8,500 on vehicle maintenance in a week. If the total income from fares for that week was N90,000, calculate the company's profit or loss for the week.
Solution: Total Expenditure: N45,000 (fuel) + N25,000 (wages) + N8,500 (maintenance) = N78,500 Income: N90,000 Result: Income - Expenditure = N90,000 - N78,500 = N11,500 Conclusion: Since the result is positive, the company made a profit of N11,500. (
Commentary: This combines multiple expenditure items common in a small Nigerian business.)
Question: A local craftswoman buys materials for N5,000 to make beads. She sells the finished beads for N6,200. a. Calculate the profit she made. b. Calculate the percentage profit.
Solution: a.
Profit: Selling Price (SP) - Cost Price (CP) = N6,200 - N5,000 = N1,200 b.
Percentage Profit: (Profit / CP) × 100% = (N1,200 / N5,000) × 100% = (12/50) × 100% = 0.24 × 100% = 24% (
Commentary: This focuses on basic profit calculation and percentage for local enterprise.)
Question: A mobile phone marked at N45,000 is sold with a 8% discount during a promotional period. What is the selling price of the phone?
Solution: Discount Amount: 8% of N45,000 = (8/100) × N45,000 = 8 × N450 = N3,600 Selling Price: Marked Price - Discount Amount = N45,000 - N3,600 = N41,400 (
Commentary: Simple discount calculation, common in electronics stores in Nigeria.)
Question: Mr. Emeka took a loan of N200,000 from a microfinance bank at a simple interest rate of 10% per annum for 2 years. How much interest will he pay back?
Solution: Formula for Simple Interest (I): (P × R × T) / 100 Substitute values: P = N200,000, R = 10%, T = 2 years Calculation: I = (N200,000 × 10 × 2) / 100 = (N200,000 × 20) / 100 = N2,000 × 20 = N40,000 (
Commentary: Direct application of simple interest formula, relevant to small loans in Nigeria.) This involves calculations related to income, expenditure, and managing finances within a personal or small business context.
Income: Money received, usually regularly, for work or through investments.
Examples: Salaries, wages, business profits, allowances, rent received.
Expenditure: Money spent on goods, services, or bills.
Examples: Food, transport, utility bills (electricity, water, waste disposal), rent paid, school fees, office supplies, salaries (for an employer).
Budgeting: The process of planning how to spend and save money, usually to ensure that expenditure does not exceed income.
Concept: Income - Expenditure = Balance (Surplus if positive, Deficit if negative).
Utility Bills: Charges for essential services like electricity, water, and waste disposal.
Electricity Bill: Often calculated based on units consumed and a fixed tariff per unit, sometimes with a service charge.
Units Consumed: Current Reading - Previous Reading.
Cost: (Units Consumed × Tariff per unit) + Service Charge (if any).
Water Bill: Similar to electricity, based on volume consumed (e.g., in cubic meters) and a tariff.
Worked Example 1 (Household Expenditure): Mrs. Okoro's family has a monthly income of N75,
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0. Her monthly expenditures are: food N40,000, transport N15,000, electricity N8,000, and miscellaneous N5,500. a. Calculate the family's total monthly expenditure. b. Calculate the family's balance at the end of the month. c. Is their budget in surplus or deficit?
Solution: a. Total monthly expenditure = Food + Transport + Electricity + Miscellaneous = N40,000 + N15,000 + N8,000 + N5,500 = N68,500 b. Balance = Income - Total Expenditure = N75,000 - N68,500 = N6,500 c. Since the balance is positive (N6,500), their budget is in surplus. Worked Example 2 (Utility Bill - Electricity): An office's electricity meter reading on May 1st was 4500 units. On June 1st, the reading was 4850 units. If the electricity tariff is N50 per unit and there is a fixed service charge of N1,500, calculate the total electricity bill for May.
Solution: Units consumed = Current reading - Previous reading = 4850 units - 4500 units = 350 units Cost of units consumed = Units consumed × Tariff per unit = 350 units × N50/unit = N17,500 Total electricity bill = Cost of units consumed + Service charge = N17,500 + N1,500 = N19,000 This section deals with calculations related to buying and selling goods and services, aiming to understand profitability and pricing.
Cost Price (CP): The price at which an item is bought or the cost of producing it. Also known as "Purchase Price".
Selling Price (SP): The price at which an item is sold to a customer.
Profit: Occurs when the Selling Price (SP) is greater than the Cost Price (CP).
Formula: Profit = SP - CP Percentage Profit: % Profit = (Profit / CP) × 100% Worked Example 3 (Profit): A trader at Onitsha Main Market buys a carton of soft drinks for N2,800 and sells it for N3,
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0. Calculate: a. The profit made. b. The percentage profit.
Solution: a. Profit = SP - CP = N3,500 - N2,800 = N700 b. Percentage Profit = (Profit / CP) × 100% = (N700 / N2,800) × 100% = (1/4) × 100% = 25% Loss: Occurs when the Cost Price (CP) is greater than the Selling Price (SP).
Formula: Loss = CP - SP Percentage Loss: % Loss = (Loss / CP) × 100% Worked Example 4 (Loss): A farmer bought a bag of yam for N12,
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0. Due to spoilage, he had to sell it quickly for N10,
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0. Calculate: a. The loss incurred. b. The percentage loss.
Solution: a. Loss = CP - SP = N12,000 - N10,500 = N1,500 b. Percentage Loss = (Loss / CP) × 100% = (N1,500 / N12,000) × 100% = (1/8) × 100% = 12.5% Discount: A reduction in the original or marked price of an item.
Marked Price (MP): The original price at which an item is displayed for sale.
Discount Amount: Discount Rate / 100 × Marked Price Selling Price (after discount): Marked Price - Discount Amount Worked Example 5 (Discount): During a festive season sale, a supermarket offers a 15% discount on a television set marked at N90,000. a. Calculate the discount amount. b. Calculate the new selling price of the television.
Solution: a. Discount Amount = 15% of N90,000 = (15/100) × N90,000 = 15 × N900 = N13,500 b. New Selling Price = Marked Price - Discount Amount = N90,000 - N13,500 = N76,500 Commission: A payment made to an agent or salesperson for selling goods or services, typically calculated as a percentage of the total sales.
Formula: Commission = (Commission Rate / 100) × Total Sales Worked Example 6 (Commission): A real estate agent receives a 3% commission on the sale of a property. If the agent sells a house for N25,000,000, how much commission does he earn?
Solution: Commission = 3% of N25,000,000 = (3/100) × N25,000,000 = 3 × N250,000 = N750,000 Simple Interest: Interest calculated only on the principal amount, without compounding. Commonly used for short-term loans or basic savings accounts.
Principal (P): The initial amount of money borrowed or invested.
Rate (R): The percentage of the principal charged as interest per year (expressed as a decimal or fraction in calculation).
Time (T): The duration for which the money is borrowed or invested, usually in years.
Formula: Simple Interest (I) = (P × R × T) / 100 (when R is a percentage)
Amount (A) after T years: A = P + I Worked Example 7 (Simple Interest): Mr. Abubakar deposits N150,000 in a fixed deposit account that offers a simple interest rate of 5% per annum.
Calculate: a. The interest earned after 4 years. b. The total amount in his account after 4 years.
Solution: Given: P = N150,000, R = 5%, T = 4 years. a. Interest (I) = (P × R × T) / 100 = (N150,000 × 5 × 4) / 100 = (N150,000 × 20) / 100 = N1500 × 20 = N30,000 b. Total Amount (A) = Principal + Interest = N150,000 + N30,000 = N180,000
Personal and Family Budgeting: Students can apply the concepts of income and expenditure to help their families create simple monthly budgets. This could involve tracking household spending on food, electricity, and transport versus family income, encouraging responsible financial habits from a young age.
Market and Shop Transactions: When students go to the market with their parents or buy items from a local shop, they can consciously apply the concepts of profit, loss, and discount. They can estimate discounts during sales, calculate the profit a small vendor makes, or understand why prices might differ. This helps them become smarter consumers.
Entrepreneurship and Small Businesses: For students interested in starting small ventures (e.g., selling handmade crafts, running errands for a fee), understanding cost price, selling price, profit margins, and potential losses is fundamental. This lesson provides a basic framework for managing the finances of a small business, a common aspiration in Nigeria.
Banking and Savings: Understanding simple interest helps students grasp how savings accounts grow over time or how interest is calculated on small loans. This can encourage them to save money or to be cautious about borrowing.