Preview Cambridge IGCSE prep

Core is not a short syllabus; it is a narrower one, and almost every mark on papers 1 and 3 comes from doing ordinary arithmetic reliably under time pressure. The number block is the largest single lever: addition and subtraction of negatives, the order of operations, factors, multiples, primes, HCF and LCM, fractions and decimals of quantities, standard form for large and small numbers, and the four families of percent work — increase and decrease, reverse percentages, compound interest over a whole number of years, and profit and loss as a percentage of cost. Marks are then taken in algebra that is entirely mechanical once the habits are set: collecting like terms, expanding a single bracket and a product of two brackets, factorising, substituting into a formula with negative values, solving linear equations with the variable on both sides, simultaneous equations by elimination, and simple inequalities on a number line. Geometry and measures are worth roughly a third of the paper and are the section most often answered in prose instead of arithmetic: perimeter and area of rectangles, triangles and parallelograms, volume and surface area of a cuboid and a prism, the circumference and area of a circle, the sum of angles in a triangle and round a point, angles in parallel lines, and the three similarities that matter at this tier: line, rotational and reflection symmetry, plus enlargement with a positive scale factor. Bearings are drawn, measured and stated as three digits. Statistics is the cheapest section on the paper — mean, median, mode and range from a list, the modal class from grouped data, and reading a bar chart, pie chart or scatter graph — and probability is a single idea: favourable outcomes over total outcomes, with the complement used to save work. Presentation carries the rest. Core papers award method marks even when the final answer is wrong, which means a line of working is never wasted; the multiple-choice paper (30% of the total) punishes the reverse, because there is nothing to show, so answers must be checked by substitution or by estimating the size of the result. Two habits fix most Core grades: write the formula before substituting, and re-read the question at the end to answer what was asked — the exact value, to the stated degree of accuracy, with units.

STANDARD FORM: a number written as A × 10ⁿ with 1 ≤ A < 10 — used for very large and very small quantities. REVERSE PERCENTAGE: finding the original amount when a percentage change has already been applied. SIMULTANEOUS EQUATIONS: two equations solved together, by making one coefficient match and eliminating. BEARING: an angle measured clockwise from north, always stated with three digits. MODAL CLASS: the interval with the greatest frequency in grouped data. ENLARGEMENT: a shape scaled from a centre by a scale factor; lengths multiply by k, areas by k².