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PSLE Math HCF Ladder Method & Hard Questions Guide
Master the HCF Ladder Method for challenging PSLE math questions. Step-by-step guides and past-year paper walkthroughs.
This guide focuses on teaching parents and students how to master the HCF (Highest Common Factor) Ladder Method to solve challenging PSLE Mathematics questions, with step-by-step walkthroughs of exam problems.
Part 1: Understanding HCF & The Ladder Method
The Concept of HCF: Highest Common Factor is the largest number that divides two or more numbers without a remainder. It is ideal for grouping or dividing items into equal sets.
The Ladder Method Structure: Draw a vertical division line and divide the numbers simultaneously by common prime factors (2, 3, 5, 7, etc.). Continue until the remaining quotients have no common factors.
Part 2: Walkthrough of 2023 Paper 1 Question 14
The Problem: Two ribbons of lengths 84 cm and 120 cm are cut into equal pieces. Find the longest possible length of each piece such that no ribbon is left over.
Step 1: Set up the ladder division for 84 and 120. Divide by 2 to get 42 and 60.
Step 2: Divide 42 and 60 by 2 to get 21 and 30.
Step 3: Divide 21 and 30 by 3 to get 7 and 10. Since 7 and 10 share no common factors, stop.
Step 4: Multiply the common factors along the left: 2 * 2 * 3 = 12. The longest possible length is 12 cm.
Frequently Asked Questions
When should my child use the HCF Ladder Method instead of LCM?▾
Use HCF when a problem asks to group, divide, or cut items into the largest possible equal sizes (e.g., cutting ribbons or grouping students). Use LCM when looking for the earliest common meeting point or time when events repeat.
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