Try this beautiful problem from Algebra based on LCM from AMC-8, 2016.
The least common multiple of $a$ and $b$ is $12$, and the least common multiple of $b$ and $c$ is $15$. What is the least possible value of the least common multiple of $a$ and $c$?
Algebra
Divisor
multiplication
Answer:20
AMC-8, 2016 problem 20
Challenges and Thrills of Pre College Mathematics
We have to find out the least common multiple of $a$ and $c$.if you know the value of \(a\) and \(c\) then you can easily find out the required LCM. Can you find out the value of \(a\) and \(c\)?
Can you now finish the problem ..........
Given that the least common multiple of $a$ and $b$ is $12$, and the least common multiple of $b$ and $c$ is $15$ .then b must divide 12 and 15. There is only one possibility that b=3 which divide 12 and 15. therefore \(a\)=\(\frac{12}{3}=4\)
can you finish the problem........
so\(b\)=3. Given that LCM of \(b\) and \(c\) is 15. Therefore c=5
Now lcm of \(a\) and \(c\) that is lcm of 4 and 5=20
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