To answer GCF and LCM questions.
You can use the numbers in common in the prime factorization to find the LCM (least common multiple of two numbers). Multiply all the prime factors together, but if the two numbers have a prime factor in common, only use that number once. Here are a few examples: Find the LCM of 40 and 35: The prime factorization of 40 is 2*2*2*5. The prime factorization of 35 is 5*7. The prime factorization both have a 5 in common, so you only need one five. The LCM then is 2*2*2*7*5 = 280. Find the LCM of 24 and 20: 24 = 2*2*2*3. 20 = 2*2*5. The prime factorization have two twos in common, so you only need one two from each pair. You will still need another 2 since the third 2 in the prime factorization of 24 does not have a pair in the factorization of 20. The LCM then is 2*2*2*3*5 = 120. Find the LCM of 15 and 4: 15 = 3*5 4 = 2*2 There are no matching pairs between the prime factorization, so find the LCM by multiplying all the numbers together: 2*2*3*5=60 Find the LCM of 60 and 100: 140 = 2*2*3*5 100 = 2*2*5*5 There are two pairs of 2s and a pair of 5. You can think of it like this: 140 = (2*2*5)*3 100 = (2*2*5)*5 The numbers in parentheses are pairs so you only need one of them. In this case, the LCM is (2*2*5)*3*5 = 300.
In finding the LCM or HCF of two or more numbers
The prime factorization of 560 is: 2, 5, and 7
Prime numbers help you to find the LCM and the GCF.
True.
You need at least two numbers to find an LCM no matter what you use.
speed you can just use your brain to find the LCM faster, sometimes.
To answer GCF and LCM questions.
To find the GCF and the LCM you have to first at least try to use prime factorization. So use factor trees. Or for the LCM find th least common multiples of the number.
It doesn't matter which method you use. You still need at least two numbers to find an LCM. There is no LCM of 20.
You can use the numbers in common in the prime factorization to find the LCM (least common multiple of two numbers). Multiply all the prime factors together, but if the two numbers have a prime factor in common, only use that number once. Here are a few examples: Find the LCM of 40 and 35: The prime factorization of 40 is 2*2*2*5. The prime factorization of 35 is 5*7. The prime factorization both have a 5 in common, so you only need one five. The LCM then is 2*2*2*7*5 = 280. Find the LCM of 24 and 20: 24 = 2*2*2*3. 20 = 2*2*5. The prime factorization have two twos in common, so you only need one two from each pair. You will still need another 2 since the third 2 in the prime factorization of 24 does not have a pair in the factorization of 20. The LCM then is 2*2*2*3*5 = 120. Find the LCM of 15 and 4: 15 = 3*5 4 = 2*2 There are no matching pairs between the prime factorization, so find the LCM by multiplying all the numbers together: 2*2*3*5=60 Find the LCM of 60 and 100: 140 = 2*2*3*5 100 = 2*2*5*5 There are two pairs of 2s and a pair of 5. You can think of it like this: 140 = (2*2*5)*3 100 = (2*2*5)*5 The numbers in parentheses are pairs so you only need one of them. In this case, the LCM is (2*2*5)*3*5 = 300.
In finding the LCM or HCF of two or more numbers
3 x 5 = 15 3 x 7 = 21 3 x 5 x 7 = 105, the LCM
The prime factorization of 560 is: 2, 5, and 7
you use prime factorization
3 x 5 = 153 x 7 = 213 x 5 x 7 = 105, the LCM