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 77 and 91 would be 143.
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 77, 91 and 143 equals 1001
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 77, 91 and 143 equals 1
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 prime factors in each number.