3 mental strategies to make math magical

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You are born either loving math or hating it – I’m sure most of you would agree with me. I was lucky enough to be born loving math, and now as a teacher of math, I feel it is my primary responsibility to make my students love math before anything else.

When do you love to do something – when you enjoy it, have fun doing it and have no fear of being judged if you go wrong, am I right ?! How can we achieve this with math?

I start the session by framing essential agreements with my students for math –

The above agreements go a long way in making students comfortable in class and willing to learn with a growth mindset. What I also do is focus on the different aspects of math – making real life connections, demonstrating mental math strategies, and engaging them with critical thinking questions

In this post I will focus on 3 of the mental math strategies that help students speed up their calculations while avoiding lengthy calculations with paper and pencil. It helps make math more fun, almost magical when you play around with numbers like this and helps develop a passion for the subject

In this post, I am highlighting 3 of the many mental math strategies I use in my classes –

Multiplying by 11 using Vedic math strategy

I love this one – it’s like magic and my students love it too!! In fact, I tell them to impress their friends and family at home by asking a question like – what’s 263 x 11, and then just instantly answering it with an abracadabra – . The answer is 2893

Let me demonstrate how to multiply with a smaller number first – 26 x 11

Write the lowest and highest place in the number as is. Here it would be 2 and 6. Then starting from the highest place, add each digit with the next place thus –

2 then 2+6 then 6 = 286. i.e. 26 x 11 = 286

Similarly 34 x 11 = 3 (3+4) 4 = 374

45 x 11 = 4 (4+5) 5= 495 and

541 x 11 = 5 (5+4) (4+1) 1 = 5951

Try this magic for yourself –

1. 431 x 11 =
2. 8103 x 11 =
3. 713 x 11 =

(All answers at the end of the post 🙂)

It works with numbers where there will be carry over too, for example

89 x 11 = 8 (8+9) 9 = 8⁺¹ 7 9 = 979 (as 8+9 = 17 the 1 gets carried over to the higher place)

Try one for yourself – 467 x 11

Double and half strategy

Suppose I need to solve 48 x 50, i would usually do it using the column method right? There is an easier way though! It is always easier to multiply by 10 / 100/ 1000 right? So double the 50 (that’s 100)and halve the 48 (that’s 24).

The value remains the same and it is so much easier to multiply 24 x 100

So, 48 x 50 = 24 x 100 = 2400

The strategy will only work when one number can be doubled to give a 100/ 1000 etc

Try a few for yourself –

1. 632 x 50
2. 450 x 500

Rearranging numbers

When you need to multiply 25 x 141 x 4, you would normally multiply 25 by 141 and then by 4 right ?

Using the associative property of multiplication I can rearrange the numbers to make my job easier – 25 x 4 x 141 = 100 x 141 = 14100 –> and voila, done mentally !!

Similarly –> 20 x 329 x 5 = 20 x 5 x 329 = 100 x 329 = 32900

Try a couple for yourself 🙂

1. 25 x 678 x 4
2. 20 x 9099 x 5

While I encourage my students to look for these patterns that will definitely make their life easier, there is always a word of caution – be comfortable with the strategy and choose the appropriate one!

Answers –

1. 431 x 11 = 4741
2. 8103 x 11 = 89,133
3. 713 x 11 = 7843
4. 467 x 11 = 4 (4+6) (6+7) 7 = 4⁺¹ 0⁺¹ 3 7 = 5137
5. 632 x 50 = 316 x 100 = 31,600
6. 450 x 500 = 225 x 1000 = 225,000
7. 25 x 678 x 4 = 25 x 4 x 678 = 67,800
8. 20 x 9099 x 5 = 20 x 5 x 9099 = 909,900

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