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Some Insights on Mind Matters - What to Learn for Quick Calculations

Mind matters is what I want to talk about today but I will have to give you some background to make my point clearer.

 

If you have read some of my posts before, I guess you will agree that I am a devoted ‘logical solution’ fan. To increase speed, I advice my students to try to solve all quant questions orally - to sit without a pen and paper and see if you can force yourself to figure out the answer without writing a word. I solve most of the GMAT relevant questions orally so it is certainly possible. If a question makes me get up and get my pen and paper and then, if I can solve the question within two minutes, I consider it a very tricky but good GMAT question.

 

But an incident happened with me a few years back which surprised me. I was studying for my CFA exam with my calculator and pen right next to me, and I found myself punching in 138 and then the division sign and then, 10. I am sure you can guess the answer I got (which was 13.8 of course) and I found myself staring at my calculator for the next few seconds. I couldn’t believe that I worked out that calculation on the calculator. I was highly intrigued by the fact that I missed the 10 in the denominator when I suggest people to develop end-to-end oral problem solving skills!

 

The point is that it is all about perception. When I see a GMAT question, my mind automatically goes to the ‘solve yourself’ mode. No matter how insane the numbers LOOK, I KNOW they will fall into place. CFA exam affords no such luxuries. The numbers are crazy and you need to use a calculator so even if you have easy numbers in front of your eyes, you just don’t register them. It’s as if it doesn’t matter what the numbers LOOK like, you BELIEVE they are complex. Then it is all about belief.

 

Can you train your mind to understand that GMAT doesn’t need pen and paper? Sure! Give up your pen/pencil right away and put it far away from you before you start doing some questions. If your writing material is far away and you are half as lazy as I am, you will try to work the question out in your mind instead of getting up to go and get your pen. You will struggle initially but you can slowly train your mind to figure out how the numbers fit in the puzzle to show you the whole picture. But before you start this exercise, there is some preparation you need to do. You need to memorize the following things:
 

Multiplication tables till 20 (e.g. 13*2 = 26, 13*3 = 39 till 13*10 = 130 etc)
Squares of all positive integers till 20 (e.g. 12^2 = 144, 14^2 = 196 etc)
Cubes of all positive integers till 10 (e.g. 6^3 = 216, 7^3 = 343 etc)
Factorials till 7 (e.g. 3! = 6, 6! = 720 etc)
All powers of 2 upto 2^10
All powers of 3 upto 3^6
All powers of 4 and 5 upto 4^5 and 5^5

 

I can’t stress the importance of these points enough. Knowing these things help you see patterns, figure out tricks in number properties questions, find prime numbers and of course, solve the question quickly.

 

Try to train your mind. You could easily end up with 15 mins to spare in the Quant section of the exam.

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