This is a discussion on Mental Calculation within the online poker forums, in the Learning Poker section; Hey! I thought it would be helpful to start a thread on mental calculation and specially a series of tips and tricks on how to 

Mental Calculation 
#1




Mental Calculation
Hey! I thought it would be helpful to start a thread on mental calculation and specially a series of tips and tricks on how to make them faster, as it is, I've come to understand, the very basis of Poker Maths. This applies to everyone playing live at least, you need to be pretty much able to make quick calculations in your head in order to maximize your victories.
I've been re searching on the topic and I found two really good ways of quickly multiply two digit numbers in your head that I wasn't aware of (I personally am quite good in maths and can understand all the hard stuff, fairly quick, but sharp and fast, onthespot mental calculations are an area that I want to develop even further and bring them to a higher level). If anyone knows good tips to quickly do sums, subtractions, multiplications, divisions, ratios, percentages, etc, in your head, feel free to share it here. So, I've come across two basic strategies (bear in mind that you need to train these if you have a little trouble reaching the results as it is, and I assure you that you'll become better and sharper over time, you'll see massive improvement in just the first week and it only goes up from there.) • 1st strategy: This first strategy works for two digit numbers multiplying by each other. Example: 34*72=_ _ _? What you do here is adding three spaces mentally or bear in mid that you'll fill three spaces. (It can reach more than 3). Then you multiply the first digit of the first number by the first digit of the second number, so: 3*7=21 So, you have: 34*72= 21_ _ Then you multiply the second digit of the first number by the second digit of the second number, so: 4*2=8 You now get: 34*72=21_8 Now you're going to multiply the 2nd digit of the 1st number by the 1st digit of the 2nd number and the 1st digit of the 1st number by the 2nd digit of the 2nd number, and you're gonna add the results: (4*7)+(3*2)=28+6= (If you want a simple way to do it in your head just do 30+6 and then subtract 2)= 34 Now you just add the 3 of the 34 to the 1 that was there, just like a you'd do on an algorithm and you have the result: 34*72=2448 • 2nd strategy: This second strategy is all about the base numbers and using them in our favour, so let's start out with using 10 as the base number as it is the easiest one. Y'all can use this rule for numbers that are fairly close to 10, for example: 13*18=? So, what we do here is basically see how much each number is above or below ten, so 13 is +3 above ten and 18 is +8 above ten. So, we have +3 +8 13 * 18=? Now we're going to add either the 3 to the 18 or the 8 to the 13 (because it's easier we'll add the 3 to the 18 which is 21, adding 8 to 13 would also be 21 but it's easier to reach that conclusion by adding 3 to 18) Which will give off: +3 +8 13 * 18=210 (We have to always add a zero to the right of the number) Then we multiply the 3 by the 8, which is 24 and add that to the 210. So, +3 +8 13 * 18=210 +24  234 Therefore, 13*18=234 You can also apply this rule for all of the other base numbers such as 20, 30, etc. BUT BEWARE, if you use 20 as a base number, for example, you're gonna have multiply the sum of the difference between the number and the base number to the other number by two (and if it was 30 by 3, etc) Example: +3 +8 23 * 28 = ? Now we have to add the 3 to the 28, which will be 31 and multiply the 31 by 2 so it'll be 62. +3 +8 So now you'll use the 62 to start off, 23 * 28 = 620 (never forgetting to add that zero) And then you multiply the 3 by the 8 just the same and add that to the 620, so: +3 +8 23 * 28 = 620 +24  644 Warning: if you're dealing with a number that goes below the base number, such as, for example, 18*26=? You are simply gonna have to apply the signal rules. So, this would be: 2 +6 18 * 26=? (If we wanted to use 20 as the base, which would be easier in this situation than using ten, for example). Now, the easiest thing to do here is to subtract 2 from the 26 (which is 24 but we're using base 20 so you need to multiply it by 2, 24*2=48) so it gets like: 2 +6 18 * 26= 480 (don't forget the zero!) And now you multiply the (2) by 6 which is 12 and instead of adding you're gonna subtract 12 from the 480, so: 2 +6 18 * 26= 480 12  468 (An easy way to do this subtraction mentally is by subtracting 10 from the 480, which is 470 and then subtract the remaining 2 from the 470, which would give 468. And here we have our result: 18*26=468 Now, onto the last part of this post. If both of your numbers are close to 50, you can totally use 50 as a base, so for example, if you've got: 3 +3 47 * 53=? What we'll do here is still subtract 2 from 53 (or add 3 to 47, it's irrelevant which one you choose cause they're both the same number, 47+3=50 and 533=50 as well) Now, an easy way to reach the number multiplied by 5 (or by 50 if you count the zero) is to multiply it by 100 first so: 50*100=5000 and to divide it by 2, so 5000/2=2500. Now you get: 3 +3 47 * 53= 2500 (the zero is already there cause we multiplied it by 50 instead of 5) And we simply do, (3)*3=(9) and subtract it from 2500 (an easy way to do this mentally is to subtract 10 and add 1), so: 3 +3 47 * 53= 2500 9  2491 This is all for this post, you can find a more indepth explanation in these videos:
Feel free to reply to this thread with your questions, and share tips and tricks you personally use to do fast basic maths at the Poker table, or simply at home (it can be on addictions, subtractions, multiplications, divisions, percentages, ratios, anything helpful to Poker really). Good luck mates!
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#2




Very good...!
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#3




If y'all wanna make multiplications of 3 digit numbers by 2 digit numbers all you have to do is apply those same rules, only in a tweaked way,
So, if you have, for example, 134*26=? What you wanna do here is look at 134 as 100+34 So you have (100+34)*26 Now you apply one of those two rules I showed you in order to solve 34*36 mentally. If y'all wanna make multiplications of 3 digit numbers by 2 digit numbers all ou have to do is apply those same rules, only in a tweaked way, So, if you have, for example, 134*26=? What you wanna do here is look at 134 as 100+34 So you have (100+34)*26 Now you apply of of those two rules I showed you to do 34*36 mentally and you get 1224. Then you do 100*26=2600 (you only have to add two zeros because you're multiplying by 100) And now you simply add both results in your head, so: (100+34)*26=1224+2600=3824 If you want to multiply by a three digit number that has a 3rd digit that's greater than 1, some easy ways to multiply by 200, 300, etc. Is to simply multiply the number by the third digit and add two zeros, so for example: 200*34=? Here you'd multiply the 34 by 2 which would be 68 and add two zeros to the right. 200*34=6800 Another types of calculations you might need to make relating to the blinds and how much you have in your stack in terms of bb (big blinds) are, for example: Let's say you're playing NL50. The small blind is $0,25 and the big blind is $0,50 and you want to set a goal to get your stack to 135 times the big blind. You'd have to do: 135*0.50 What you do here to solve this calculation is basically treat the 0.50 like it was 50 at first, so you do: (100+35)*50=5000+1750=6750 What you do now is simply add the two decimal houses of the 0.50 and so you get your answer of: $67,50 So you need a $67,50 dollar stack to have 135 times the bb and so what many consider a considered deep stack!
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