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 This topic has 4 replies, 2 voices, and was last updated 1 year, 6 months ago by Abhishek R.

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December 22, 2019 at 7:20 pm #8881
I have a couple of suggestions for this book and problems that I have,
1. First suggestion, I noticed the all 9, last 10 in Chapter 8 was thought right to left instead of left to right. Let’s say we have 892. It would have said to first find the last digit. Then. the rest of the digits (going right to left) should add to 9. You would first get 8, then 08, finally 108.
2. Next suggestion, I think the book should expand to working with fractions, decimals, percentages, cubes, fourth and fifth powers, and square and cube roots. In addition, the book doesn’t work too much with negative numbers. I really love your teaching style and lectures, so it would be a help to more people if we can work with more complicated stuff.
3. Moving on to questions, how do you keep problems for a brief moment in your head? I have lots of success with two digit numbers in arithmetic, but three digit and four digit numbers complicate my mind, so I cannot hold the problem for long. I cannot think of a good memory palace or replacing numbers with objects to hold these.
4. Another question, the practice exercises in the book for multiplication by 11 stresses me out. For instance, doing 9581 X 11 requires lots of carryovers. Sometimes I even have to go back to make sure I am correct because I want to be as correct as possible. How would you solve this problem? Does rounding help it out?
5. Also, when doing simple arithmetic such as 72 X 9. I feel tempted to go right to left instead of left to right. Often, I would force myself to do it, but I end up still doing it right to left. Is there any alternatives for resisting doing arithmetic right to left?
6. Just for future reference, is there any instances where the DS and DD won’t catch the wrong answer to arithmetic? Is there any other checking methods to cover this problem up or will we have to rely on reasonablity to check it?
By the way, the book is really good! Thank you for taking your time into reading this and happy holidays!
December 23, 2019 at 1:57 am #8882Hi Aarin,
Thank you for taking the time to write suggestions.
1. I didn’t quite understand the first suggestion. Are you saying we teach to calculate from right to left in Chapter 8?
2. For the second point on including percentages, fractions etc, I will add it to my backlog and will work to incorporate it into the book and course. I have purposely kept some of the more complicated stuff out of the book so that it remains relevant to most people reading the book or watching the course. I will try to create a course companion so that it becomes useful.
3 & 4. For the next two points which are sort of interlinked which is to remember numbers in your head and carrying over numbers, I would encourage you to read this community post – https://ofpad.com/topic/isonlythecalculationperformedinthemind/
It probably has the exact answer that you are looking for. Let me know if it doesn’t answer the question.5. Remembering to calculate from left to right comes with practice. If you do it enough number of times, it will become the only natural way to do mental math.
6. The only way to be 100% sure is to of course do the math problem again. Both methods rely on estimation and has an accuracy of >90%. Using both methods together will increase the accuracy even further because the chances of both methods not catching it combined is pretty slim. If I find a method that has even more accuracy, I will make sure I include it.
Let me know if this answers all your questions. If you do enjoy the book, please don’t forget to leave a review. It is really helpful to reach more students.
December 24, 2019 at 6:46 pm #8886I am talking about the method to find how much you rounded up. It is taught right to left.
Also, could you add geometric and trig functions to your backlog if you want to.
The post helped for 3, but not 4.
Another question, if numbers get large (e.g. 169,523), how could you multiply them with another large number using the UT, Bridge, or Virtuvian Man method, with very little mental stress?
That is all I have to say. Happy holidays!
December 29, 2019 at 3:43 pm #8907Can you reply to my last post?
December 29, 2019 at 5:09 pm #8909Hi Aaron,
The round up method simply states that the last digits add up to 10 and the other digits add up to 9. There is no concept of left to right or right to left here. So was not sure what you meant?
Can you give me an example of what kind of scenarios you will need to do mental math for trigonometry or geometry? Those are generally not areas where we need to do mental math in the real world or in exams.
Multiplying large numbers come with practice and using the mind palace. You have to use a combination of rounding up and the methods we have covered to do the mental calculation. It will not be as easy and fast as multiplying lower digit numbers.

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