Key Changes in the H2 Math Syllabus (9758)

LCM Least Common Multiple
LCM Least Common Multiple

What is the Least Common Multiple (LCM)?

The Least Common Multiple (LCM) of two or more whole numbers is the smallest positive number that is a multiple of all the given numbers.

 In simpler terms, it’s the lowest number that all the original numbers can divide into without a remainder.

 

🔢 Example:

To find the LCM of 4 and 6:

  • Multiples of 4: 4, 8, 12, 16, …

  • Multiples of 6: 6, 12, 18, …

  • The LCM is 12 (the smallest common number in both lists).

Where is LCM Tested?

In Singapore’s education system, LCM is tested at several levels:

Primary School (P4 to P6)

Usually taught together with Highest Common Factor (HCF).

Appears in word problems involving:

– Events happening at regular intervals (e.g., “When will two buses next arrive at the same time?”)

– Time-based problems

This topic is included in PSLE Mathematics.

 

Lower Secondary Mathematics (Sec 1 Express / N(A))

– Reinforced again as part of number theory, typically in early algebra topics.

– Used in simplifying fractions, solving ratio and rate questions.

 

Foundation for Higher Topics

  • Although not directly tested in upper secondary or A-Level Math, understanding LCM is essential groundwork for:

    • Algebraic manipulation

    • Common denominators in equations

    • Number patterns and sequences

 

LCM Questions to Try Out (For Primary Math Students)


🟢 Basic Level (P4–P5)

Q1. Find the LCM of 3 and 5.

Q2. What is the least common multiple of 4, 6, and 8?

🟡 Intermediate Level (P5–P6, PSLE-style)

Q3. Amy exercises every 6 days, and Ben every 8 days. If they both exercised today, in how many days will they exercise on the same day again?

Q4. A bell rings every 12 minutes and another bell rings every 18 minutes. If both bells ring together at 9:00 AM, what time will they next ring together?

🔴 Advanced Level (P6–Sec 1)

Q5. Three buses leave a terminal at the same time. The first bus returns every 20 minutes, the second every 30 minutes, and the third every 45 minutes. After how many minutes will all three buses be at the terminal together again?

Q6. Two LED lights blink at intervals of 24 seconds and 36 seconds. If they blink together at 6:00 PM, how many times will they blink together again before 7:00 PM?

Q7. Find the LCM of 36 and 120 using prime factorisation.

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