# Lcm and GCF of 20 and 30

The GCF or greatest common factor is the largest positive integer that will divide into each number evenly or in other words a remainder of zero
For example, the greatest common factor of 5 and 10 would be 5.
There are several different names for the GCF ( greatest common factor)
GCD Greatest Common Denominator
HCF Highest Common Factor
GCD Greatest Common Divisor

The GCF for 20 and 30 equals 60

The lcm or least common multiple is the smallest positive integer that two or more numbers will divide into evenly. Again, a zero remainder.

Other names for the LCM

LCD Least Common Denominator
LCD Least Common Divisor

The LCM of 10 and 20 equals 10

I like to use a factor tree to find the LCM and the GCF

Once you find all of the prime factors of a number, to find the GCF you multiply all of the factors, but multiply duplicates in each number only once.

In order to calculate the LCM you look for factors in each number.

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