
Math General Math Forum  For general math related discussion and news 
 LinkBack  Thread Tools  Display Modes 
April 11th, 2015, 11:40 AM  #1 
Newbie Joined: Apr 2015 From: United Kingdom Posts: 1 Thanks: 0  Tricky HCM and LCF question:
Hi, I got really stuck with this question and I would really appreciate some help on how to work it out: Martin thinks of 2 numbers. He says the HCF of the 2 numbers is 6 and the LCM is a multiple of 15. Write down the 2 possible numbers that Martin is thinking of: 
April 11th, 2015, 12:05 PM  #2 
Global Moderator Joined: Dec 2006 Posts: 18,059 Thanks: 1396 
Each number is divisible by 6 and just one of the numbers is divisible by 5, so the numbers are 6m and 30n, where m and n are any natural numbers whose HCF is 1. Do you now understand why?

April 11th, 2015, 01:42 PM  #3 
Senior Member Joined: Jan 2014 From: The backwoods of Northern Ontario Posts: 371 Thanks: 68 
An algorithmic techique: Choose the HCF for the first number. To get the second number, factor the HCF and the LCM 6=2×3 15=3×5 Put a stroke through the common factors, in this case the two 3s. Now write out the factors as a product, counting the 3s just once: 2×3×5=30 The second number is 30. Another example: Find two numbers such that the HCF is 20 and the LCM is 30. Answer: The first number is 20. 20 = 2×2×5 30 = 2×3×5 The second number is 2×2×3×5, that is 60. 

Tags 
hcm, lcf, maths, question, tricky 
Search tags for this page 
hcf of two numbers is 6 and lcm is 15,lcf and HCM,hcm maths,HCF and LCM of 6 and 15,lcf maths,lcf and hcm,LCF in maths,lcf hcm,hcm lcf,hcm math,Find the LCF of 30?,HCM,LCF,hcm and lcf,Lcf maths qus,math l cf hcm
Click on a term to search for related topics.

Thread Tools  
Display Modes  

Similar Threads  
Thread  Thread Starter  Forum  Replies  Last Post 
A even more tricky question  wuzhe  Algebra  0  November 30th, 2012 05:30 PM 
tricky Geometry question....  wuzhe  Geometry  6  December 20th, 2011 03:19 PM 
tricky Set related question  ikurwa  Applied Math  4  June 28th, 2011 06:23 AM 
Tricky test question  cknapp  Real Analysis  3  October 14th, 2009 12:08 PM 
Tricky question for me  Hioho  Advanced Statistics  2  May 15th, 2008 05:24 AM 