Prime Factors, HCF & LCM (Edexcel IGCSE Maths A (Modular): Foundation Unit 2): Exam Questions

Find the Highest Common Factor (HCF) of 140 and 245.

A machine has a buzzer that sounds every 50 minutes.
The machine also has a bell that sounds every 80 minutes.

The buzzer and the bell sound together at 10 am.

Find the time at which they next sound together.

Write 300 as a product of its prime factors. Show your working clearly.

$A=2\times 2\times 2\times 3\times 3\times 5$

$B=2\times 2\times 3\times 3\times 3\times 5$

Find the lowest common multiple (LCM) of $5A$ and $7B$
Show your working clearly.

$A=5^3\times 7^3\times {11}^6$ and $B=5^6\times 7^2\times {11}^4$

Find the highest common factor (HCF) of $A$and $B$
Give your answer as a product of powers of its prime factors.