Index Numbers, Glossary

Knowing the vocabulary of Index Numbers precisely is worth easy marks in SPM Add Math. Questions often turn on a single keyword, read it correctly and the method follows; misread it and even good algebra earns nothing.

Because the SPM paper is bilingual (BM/EN), each term below shows the English and Malay wording, so your child recognises it whichever way a question is phrased.

• Index Number, An index number measures how a quantity has changed relative to a reference level, expressed as a percentage of that base without a unit. It compares values across time or place, and a value above 100 shows an increase from the base while below 100 shows a decrease. →
• Price Index, A price index is an index number showing how the price of an item has changed from a base period, calculated as $\frac{\text{price in given period}}{\text{price in base period}}\times100$. For example, a price index of 120 means the price has risen by 20% since the base period. →
• Composite Index, A composite index combines several individual index numbers into one overall figure, using weights to reflect the relative importance of each item. It is calculated as $\bar{I}=\frac{\sum I_i w_i}{\sum w_i}$, giving a single measure of change for a whole basket of items. →
• Weightage, Weightage is a number assigned to each item in a composite index to show how important it is relative to the others. Items used more heavily receive larger weights, so they influence the overall index more. Weights may be given as ratios, percentages, or quantities. →
• Base Year, The base year is the reference period against which all other values are compared in an index number, and its index is set to 100. Changes are measured relative to this year, so choosing a stable, typical base year makes comparisons meaningful and easy to interpret. →

Do not just memorise definitions, practise using each term inside a full solution, the way a marker expects to see it. In the Index Numbers chapter especially, stating the right definition or condition in your working can itself earn a method mark.

Our teachers check that a student can both recall a term and deploy it fluently under exam conditions.

Vocabulary sticks best when it is tied to doing rather than reading. Instead of learning the Index Numbers terms as a flat list, meet each one inside a worked question and say the step aloud in words as you write it, a term you can use in a sentence is a term you understand.

It also helps to link related terms together rather than in isolation, since Index Numbers questions usually combine several ideas at once. Because the SPM paper is bilingual, glance once at the Malay and English wording of each term side by side, so the language a question is set in never throws you.

If a term keeps feeling slippery, that is usually a sign the underlying idea needs another look, not the word itself, and that is exactly the kind of gap a one-to-one lesson closes quickly.