Is it necesssary to use only prime factors while finding the LCM?

Answer 1

No, it is not necessary.

First, find the GCD (sometimes called the HCF). There are ways of doing this without factoring either number.

Then, divide the GCD into one number, and use the result to multiply the other number. The result is the LCM.

For example 2223 and 663 :-

2223 - 663 = 1560, 780, 390, 195
663 - 195 = 468, 234, 117
195 - 117 = 78, 39
117 - 39 = 78, 39.

The GCD of 2223 and 663 is 39. Their LCM is 2223 * 663 / 39 = 37791. The sum is easier to work out if you do the division before the multiplication.

Answer 2

ok so the GCF is the greatest common factor!! so is the largest number that goes into both numbers what i do is take the smallest number and see if it fits exactly into the larger number! 4 / 2 = 2 This does!! therefore the GCF is 2!! as both can be divided by 2! 4/2 = 2 and 2/2 = 1 The LCM is the lowest common multiple!! so the smallest number that both numbers go into!! for this i do exactly the same technique!! 4 / 2 = 2 however because we want the LCM not the GCF it is 4 because they both go into that! 4*1 = 4 and 2*2 = 4 ok for this 1, factors of what, did you mean? but il show you how its done any way and you can adjust it! if it is 8 for example then you find all the factors of 8: 1,2,4,8 and you add these together!! 1+2+4+8 = 15 threfore the total of all the factors of below 8 is 15! the largest prime fatcor of 12, you prime factorise 12, my method of this is the tree spliting it into its factors and stoping when you reach a prime number on each branch! these are 2,2,3 the largest of these is 3 therefore the largest prime factor of 12 is 3!! hope that helps!!xx

Answer 3

Yes.


Doug

Answer 4

Pretty sure no.