🔢 Commercial Mathematics
A bill/invoice lists items, prices, taxes, and total amount
▶ Play Door 21Bills, Invoices, and Banking Basics
What is a Bill or Invoice?
A bill (or invoice) is a document that lists items purchased, their prices, quantities, and the total amount due. It is issued by a seller to a buyer.
Components of a Bill:
• Date of purchase
• Item description and quantity
• Rate (price per unit)
• Amount (quantity × rate)
• Subtotal (sum of all amounts)
• Taxes (GST, sales tax, etc.)
• Total amount (subtotal + taxes)
What is Banking?
Banking involves keeping money safe in a bank account, earning interest, and making payments. Common account types:
• Savings Account: For daily transactions; earns low interest
• Current Account: For businesses with many transactions; no interest
• Fixed Deposit (FD): Lump sum for fixed period; higher interest
Key Banking Terms:
TermMeaning
Principal (P)Amount deposited or borrowed
InterestExtra money earned on deposits
Simple Interest…
Worked example
Problem: Calculate the total amount of a bill with: 3 shirts at ₹450 each, 2 pants at ₹800 each, and GST 8%.
- Shirts: \(3 × 450 = ₹1350\)
- Pants: \(2 × 800 = ₹1600\)
- Subtotal = \(1350 + 1600 = ₹2950\)
- GST = \(8% of 2950 = 8/100 × 2950 = ₹236\)
- Total = \(2950 + 236 = ₹3186\)
Answer: Total = \(2950 + 236 = ₹3186\)
Savings and Budgeting
What is a Budget?
A budget is a plan for how to spend and save money. It helps track income (money coming in) and expenses (money going out).
Parts of a Budget:
PartDescription
IncomeSalary, allowance, gifts, earnings
Fixed ExpensesRegular costs (rent, bills, loan payments)
Variable ExpensesChanging costs (groceries, entertainment)
SavingsMoney set aside for future goals
Emergency FundSavings for unexpected needs
The 50/30/20 Rule for Budgeting:
• 50% for Needs (rent, food, utilities)
• 30% for Wants (entertainment, dining out)
• 20% for Savings & Debt (savings account, loan payments)
Why Save Money?
• Emergency fund (medical, car repairs)
• Short-term goals (buying a bike, laptop)
• Long-term goals (college, house down payment)
• Future financial security
Simple Savings Plan:
• Decide a savings goal
• Calculate how much to save each month
• Set up…
Worked example
Problem: A student earns ₹2000 pocket money per month. He spends ₹800 on food, ₹300 on travel, ₹400 on entertainment, and saves the rest. How much does he save per month?
- Total expenses = \(800 + 300 + 400 = ₹1500\)
- Savings = Income - Expenses = \(2000 - 1500 = ₹500\)
Answer: Savings = Income - Expenses = \(2000 - 1500 = ₹500\)
Currency Conversion and International Concepts
What is Currency Conversion?
Currency conversion is the process of changing one country's money into another country's money using an exchange rate.
Exchange Rate:
The price of one currency in terms of another. Example: \(1 USD = ₹83.50 INR\)
Types of Exchange Rates:
TypeMeaning
Direct QuoteDomestic currency per unit of foreign currency (₹ per 1)
Indirect QuoteForeign currency per unit of domestic currency ( per ₹1)
Buying RateBank buys foreign currency from you
Selling RateBank sells foreign currency to you (higher than buying rate)
Common Currencies and Symbols:
CountryCurrencySymbol
IndiaIndian Rupee₹
USAUS Dollar
United KingdomBritish Pound£
EuropeEuro€
JapanJapanese Yen¥
ChinaChinese Yuan¥
Currency Conversion Formula:
\[
Amount in foreign currency = Amount in domestic currency × Exchange rate
\]
Factors Affecting Exchange Rates:
• Demand and supply…
Worked example
Problem: If \(1 USD = ₹83.50\), how many rupees will you get for \(250 USD\)?
- Amount in INR = \(250 × 83.50 = ₹20,875\)
Answer: Amount in INR = \(250 × 83.50 = ₹20,875\)