ISLAC International Exam Prep

You already know that when the price of something goes up, people buy less of it. But by how much less? That single question is worth a surprising number of marks in IGCSE and O-Level Economics, and the tool that answers it is price elasticity of demand . This guide covers everything you need for the exam — the formula, how to read the answer, what makes demand elastic or inelastic, and the all-important link to a firm's revenue. Why the Law of Demand isn't enough The Law of Demand tells us that, ceteris paribus, a rise in price causes a fall in quantity demanded. That's the direction of the change. What it doesn't tell us is the size — and the size is what matters to a business deciding whether to raise its prices, or to a government deciding what to tax. What is price elasticity of demand? Price elasticity of demand (PED) measures how responsive the quantity demanded of a good is to a change in that good's own price. Picture an elastic band: some goods stretc...

Forces and motion is one of the highest-scoring topics in IGCSE Physics — and it all rests on three short rules written by Isaac Newton. Master them and you can explain almost any motion question in your exam. Sir Isaac Newton (portrait by Godfrey Kneller, 1689 — public domain, Wikimedia Commons) What is a force? A force is a push or a pull, measured in newtons (N) . Force is a vector — it has size and direction — so we draw forces as arrows. Always start with a free-body diagram : the object as a box with every force shown as a labelled arrow. Balanced vs unbalanced forces When forces are balanced , the resultant force is zero . When they are unbalanced , a resultant force remains. Add forces in the same direction and subtract those in opposite directions to find it. Newton's First Law (Inertia) An object stays at rest, or keeps moving at constant velocity in a straight line, unless a resultant force acts on it. Balanced forces mean the motio...

Every computer, phone and games console makes billions of decisions every second — using nothing but 1s and 0s . The components that make those decisions are called logic gates . This lesson covers all six gates you need for IGCSE / O-Level Computer Science, their truth tables, Boolean notation, and how to combine them into real circuits. AND OR NOT Binary: 1 and 0 In digital logic, 1 = TRUE / ON / HIGH voltage, and 0 = FALSE / OFF / LOW voltage. Every input and output of a logic gate is always one of these two values. What is a logic gate? A logic gate is an electronic component with one or more binary inputs and exactly one binary output . It follows a fixed rule, described by a truth table — a list of every input combination and the output it gives. The six logic gates Gate Rule Notation NOT Flips the input (0 to 1, 1 to 0) NOT A AND Output 1 only if all inputs are 1 A · B OR Output 1 if any input is 1 A + B NAND AND, then inverted (0 only if all 1s) N...

Quadratic equations appear on almost every IGCSE Maths paper, so solving them quickly and accurately is worth a lot of marks. This lesson covers the two methods you must know — factorising and the quadratic formula — plus the discriminant and what the solutions mean on a graph. What is a quadratic equation? A quadratic is any equation where the highest power of x is 2. In standard form it looks like ax² + bx + c = 0 , where a, b and c are numbers and a ≠ 0. Your first step in any question is to rearrange it into this form. What "solving" means The solutions (or roots ) of a quadratic are the values of x that make it equal to zero. On a graph, they are exactly where the U-shaped parabola crosses the x-axis. Most quadratics have two roots. Method 1 — Factorising Factorising uses one key idea: if two things multiply to give zero, at least one of them must be zero. When the coefficient of x² is 1, find two numbers that multiply to c and...

Why do some products sell out while others — just as good — sit on the shelf? The answer is almost always the marketing mix . For IGCSE and O-Level Business, the 4 Ps are one of the highest-value topics you can master: they appear again and again, and examiners love to test whether you can apply them to a real business. What is the marketing mix? The marketing mix is the combination of decisions a business controls to persuade customers to buy, summarised as the 4 Ps: Product, Price, Place and Promotion . Get all four right — and working together — and the product sells. Why the four Ps must be balanced The Ps are interdependent : change one and the others must adjust. A premium price needs premium quality and exclusive places to sell it. Cut the price and you may need to cut costs in the product too. If the Ps don't match, customers get a confusing message. P1 — Product The good or service itself. Businesses compete on function, quality, design...

Demand and supply is the core model of microeconomics — and one of the most heavily tested topics in IGCSE Economics. Get it right and you can explain how almost any price in the real world is set. This lesson covers the demand and supply curves , the difference between a movement and a shift , and how markets reach equilibrium . What is a market? A market is any arrangement that brings buyers and sellers together. Goods flow one way; money flows the other. Demand and effective demand Demand is not just wanting something. It must be backed by the ability to pay — that is effective demand . The law of demand says that, all else equal, price and quantity demanded move in opposite directions. Plot price against quantity and the demand curve slopes downward from left to right. Movement vs shift (demand) A change in the good's own price causes a movement along the curve — an expansion or contraction of demand. Anything other than the good's own pri...