# Least Common Multiplier or LCM. What is that and why children need to know that?

I mentioned in my previous posts that my child did not really take a deep thinking while she was introduced to the topic of fractions adding. So when she told to me that they learnt to add fractions and it was very easy I asked her to add 1/12+1/3, she started to multiply 12 by 3… Not a very good sign…

I would like to mention once again that I really liked the fact that just one or two days before my child declared over the dinner that now she could add fractions she practised to find LCMs as a homework couple of days before… Very clever was my thought. But unfortunately the homework was set as a test, so you needed to choose the correct answer. And the problem here is that smart child can work out the right answer without any understanding of Least Common Multiplier. So we have here some variation of “Woe from Wit”, which Griboedov discussed couple of centuries ago… More details to follow.

We have a parental conference last Friday and the teacher gave us the test the whole class wrote. Once again I would like to point out that test itself was compiled in a very clever way. Questions 23–26 were devoted to writing numbers 25,80,135 and 44 in Product of Prime Factors from using indices and in questions 27–30 it was written “Using answers from above to assist work out the Highest Common Factor and Lowest Common Multiple of” pair of the numbers from Questions 23–26.

But because it was 77 questions in the test and very limited amount of time… and obviously no deep understanding of what she is doing…

My child started to access the problem of finding LCM of 80 and 135 as a new one…

Do not make you completely bored I will put once again definition of LCM and practical “mathematical recipe” for finding LCM of two or more numbers in a separate post. Thanks for reading. :)