Study notes and exam tips for business subjects, written by PY Education tutors — covering BAFS, Economics and more.
Changing the subject means rewriting a formula so the letter you want stands alone on one side. This note explains why you do the same thing to both sides, how to undo operations in reverse order, and works three examples — including one where the new subject appears twice.
You do not need to memorise the laws of indices — count the bases and they follow. This note derives the five laws, explains zero and negative indices, and works two examples: simplifying with positive indices, and multiplying in scientific notation.
If it costs you nothing, is it a free good? Free Wi-Fi and the tissues on the table are economic goods. One test at a price of zero draws the line, and shows why the same thing can fall on either side of it.
A limited company is a separate person in law, so the company's debts are its own. From legal personality to limited liability, then private companies against public ones — and why limited liability does not make the risk disappear.
Goods that come back cannot simply be deducted inside the purchases or sales account. This article covers how the two returns accounts are recorded, why they exist at all, and closes off Tai Shing Trading Company's April to show how returns move receivables and payables.
A trade-off is what you gave up. An opportunity cost is what the most valuable of those was worth. Most students treat them as one thing. One Saturday in Ken's life separates them, and shows why doing nothing has a cost too.
Bringing in a partner fixes the capital and the workload straight away, but unlimited liability does not go away — it becomes joint and several, so a creditor can pursue one partner for the whole debt. From what a partnership is to joint and several liability.
Not everything a company buys is a purchase, and not everything it sells is a sale. Six April transactions from Tai Shing Trading Company show how to tell purchases from assets and expenses at a glance, and why one wrong entry carries all the way through the income statement.
One person puts up the money, makes every decision and carries every risk. The sole proprietorship is the commonest form of business in Hong Kong and the one where risk is most concentrated. From business registration to unlimited liability, with the advantages and drawbacks set out in full.
Trade receivables and trade payables are not single accounts. Each is the total of a set of personal accounts. This article reads one customer's account from the start of a month to the end, then shows how both names reach the statement of financial position.
The same shop earns $340,000 in an accountant's eyes and $48,000 in an economist's, and neither of them has made a mistake. This article works through the $292,000 that separates accounting cost from economic cost, and which one the exam wants.
One kind of cost hurts when you hand the money over. The other never makes you open your wallet, and is still a cost. One year of a snack shop's figures shows how to count both, and why missing the second one loses the whole question.
How many different businesses does a grain of rice pass through on its way from the field to your bowl? This article works through primary, secondary and tertiary production, then opens up commerce into trade and the aids to trade.
Once you can tell a credit transaction apart, the next step is recording it. One full example works through a credit purchase, a credit sale, both settlements and a vehicle bought on credit in T-accounts, then reads the balances off the personal accounts.
The question the last article ended on: if the restaurant has already paid a full year's rent, does that rent count as a cost? It does not. This article explains how to spot a sunk cost, why a rational decision always ignores it, and the trap the exam likes to set.
Ask a BAFS student what business is and most will say "making money" — which earns no marks. This first article starts from human wants, defines business, goods, services and profit, and then breaks a company down into its six business functions.
Cash transactions settle on the spot, but most real business runs on "goods now, payment later". This note explains how credit transactions work, what trade receivables and trade payables are, and how to analyse the four most common credit transactions.
Knowing the definitions is one thing; using benefit and cost on an exam question is another. Two everyday examples and one common exam angle show how marginal benefit and marginal cost actually get used.
Opportunity cost — the highest-valued option forgone — is among the most examined ideas in economics. Starting from rational choice, this note shows how to identify it, how to count it, and the traps students fall into.
In economics, benefit is the satisfaction gained from consumption — and it need not be a number. This note explains how economists understand benefit, and how to compare and rank the benefit of different options.
Scarcity is where economics begins: unlimited wants meeting limited resources. This note explains wants, resources and scarcity through everyday examples — the first lesson of the PY100 economics series.
Once you can identify cash transactions, the next step is recording them. This note shows how each one lands in the T-accounts, building the bookkeeping habits the rest of the subject depends on.
Cash transactions — settled purely with cash in hand or at bank — are the first kind a company meets. This note walks through the common cases, setting up the T-account recording in the next article.
Double entry is the foundation the whole subject stands on: every transaction is recorded in two accounts, debit left, credit right. This note sets out the rules and how to decide which account to debit and which to credit.
How does equity grow? Extending the accounting equation, this note explains the link between capital and equity, and how a rise in assets or a fall in liabilities feeds through to owners’ equity.
After assets come the other two elements of the accounting equation. This note explains liabilities — obligations to be settled in future — and equity, the residual left once liabilities are deducted from assets.
An asset is the first element of the accounting equation. This note unpacks the definition — a resource controlled through past events that brings future economic benefit — and shows how to tell what counts as one.
