Sab Theek Ho Jayega !

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Kochi / Ernakulam, Kerala, India
A Doctor who loves to Live, Love and Laugh with the World! Absolutely crazy about Cricket ! Other Qualifications: A Tired Bathroom Singer, Retired Gully Cricketer and Satire Writer !

Monday, March 26, 2012

Multiply from Left to Right: Eco-friendly Mathematics !

After assisting my daughter to "Love Maths" I have decided to indulge in Mathematics because that has always been a favorite subject. If this sharing helps people, that should be wonderful. I am mostly dealing with simple Mathematics here, because I believe in beginning from the foundation. If this endeavor proves to be useful, I shall dive deeper into this in future with a series of short articles.

Yesterday Piya was struggling with 'Pi' diagrams. I don't understand why the texts and the so called guides [I would call them misguides] make it so convoluted and so tough. A simple act of multiplication for a Class 6 or 7 or 8 student is made so complicated by the texts.

I have a problem with doing addition and multiplication from right to left. It is cumbersome, time consuming and downright unintelligent. Addition and Multiplication should be done left to right; just like we write and most of this world writes.

How do we go about it ? In reality, we don't even need a paper and pencil to do multiplication of two digit numbers and three digit numbers. Honestly, this isn't any new or revolutionary idea. It just is that most of our education simply doesn't encourage using the mind or the brain. 

Kids are encouraged and even forced to learn all things by heart. We used to call that 'mugging' in the Medical College. There can't be a better word to describe this system. We are 'mugging' the thinking ability of our kids. Let me explain how we go about it. 

For a beginning, let us take a multiplication of 137 X 25. 
Our books teach us to multiply 137 X 5
And then 137 X 2 and then add the second number one place to the left to get the answer. 
We have to begin by multiplying 7 X 5
And move with the product to left and add it to 3 X 5
And then move further left and add the next product to 1 X 5. 
Then we multiply 137 X 2 similarly and add the product one place to the left. 
Most of the kids get confused here.

Now let us do it from left to right. 
For this, we use the simple formula of,
A X B = [u + v + w] X B = [u X B + v X B + w X B]. 
Here [u + v + w = A]

Let us make it simpler. 137 = [100 + 30 + 7]. 
So what do we have ? 
[100 + 30 + 7] X 25.
Now look at the answer: 2500 + 750 + 175 = 3425. 

This splitting, multiplying and adding is all done in the mind once we develop the practice. 
Right to left Maths can never be done in the mind so easily.

If we teach our kids to learn multiplication tables with proper technique, Maths becomes a cakewalk. There is no point in mugging up tables. We have to help them to understand multiplication table is nothing but adding the same number as many times as the second number suggests. By doing away with papers, we can save a lot of trees too. Thus Mathematics becomes Eco-friendly !

Dr. Punned-it


  1. Iam a dud in maths but am amazed at ur inteligence

    1. Hari Sir, I am nothing. This is just simple Maths. It just is that I am immensely lazy and try to find out easier ways to do things. And I embrace whatever is simple and easy :-)

  2. Nice Gov..yes, it is easy to do mental arithmetic once you get a hang of it. However, you need to remember tables!! So mugging does have some value. As for the "traditional" addition and multiplication from right to left, it is not that bad either. Sure it is a mechanical activity which is likely to produce correct result for a larger number of pupils..

    1. Deep, to a large extent, addition and multiplication are the simplest activities we get to do. We need our foundation right to be able to do Maths in the mind. Mugging doesn't help us to remember tables. The understanding that we are actually adding the same number as many times helps. For example, 19 x 9. Mugging up the table is NOT always necessary. We were taught to do it this way:
      19 x 10 = 190
      Just delete 19 from that = 171. It is quicker if you don't have paper and pencil. Once it becomes a habit, you'll rarely need a pencil.

      I don't 'remember' tables !

  3. what is scientific notation
    Scientific Notation include in the mathematics course. In the world of science some time we deal with numbers which are very small and those which are very large. In some branches of science large numbers while in others very small numbers are used.


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