Least Common Multiple

The least common multiple, or LCM, of two numbers is the smallest value divisible by both the numbers, or it’s the smallest number that both your numbers divide into evenly.

The LCM can be found by finding the GCF, or greatest common factors, and the remaining factors. The LCM is the product of the GCF and those remaining factors.

Mini-test: Least Common Multiple 

What is the least common multiple (LCM)  among 3, 4, and 6?
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B.
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What is the least common multiple (LCM)  among 5, 6, and 12?
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B.
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D.
E.
Which trio offers the least common multiple (LCM)?
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B.
C.
D.
E.
What is the least common multiple (LCM)  among 3, 4, and 6?
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B.
C.
D.
E.
What is the least common multiple (LCM)  among 5, 6, and 12?
A.
B.
C.
D.
E.
Which trio offers the least common multiple (LCM)?
A.
B.
C.
D.
E.

 

Next Lesson: Multiples

The transcript is for your convenience
For example, if we wanted to find the LCM of 18 and 30, we would first need to factor them. 18 is 2*9. Since 9 is not prime, we would factor to 3*3.

30 is also even, so we’ll start with 2. 30 is 2*15, 15 is not prime, so we factor 15. 15 is 3*5.

The GCF, or greatest common factor, is 2*3, or 6.

So, our least common multiple is the product of our GCF, 6, and the remaining factors. The remaining factors are 3 and 5, so 6*3*5. 6*5 is 30, 30*3 is 90. So, the smallest number that 18 and 30 will both divide into evenly is 90.

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