Least Common Multiple (LCM) (Grade 6)
A multiple of a number is what you get by counting by it (multiples of 4: 4, 8, 12, 16…). The least common multiple of two numbers is the smallest number that is a multiple of both. List the multiples of each and find the first one they share. The LCM is exactly what you need to find a common denominator when adding fractions.
Understanding least common multiple
A multiple of a number is what you get by counting by it (multiples of 4: 4, 8, 12, 16…). The least common multiple of two numbers is the smallest number that is a multiple of both. List the multiples of each and find the first one they share. The LCM is exactly what you need to find a common denominator when adding fractions.
Key Idea
A multiple of a number is what you get by counting by it (multiples of 4: 4, 8, 12, 16…). The least common multiple of two numbers is the smallest number that is a multiple of both. List the multiples of each and find the first one they share. The LCM is exactly what you need to find a common denominator when adding fractions.
Seeing it in action
Worked example
Find the LCM of 4 and 6.
Multiples of 4: 4, 8, 12, 16… Multiples of 6: 6, 12, 18…
The first shared multiple is 12.
12 is the first shared multiple of 4 and 6.
Try a few
LCM of 3 and 5
LCM of 4 and 8
LCM of 6 and 9
Factor Fields
A calm number-theory game for factors, multiples, primes, GCF, and LCM.
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Put the reasoning on paper.
Try six fraction, angle, perimeter and area questions with explained answers, for grades 4–6.
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