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The easiest and shortcut methods to do math using only human brain.....
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#1
3 January 2012 - 12:18 PM
Mental Math 
Quark
The easiest and shortcut methods to do math using only human brain.....
Mental Mathwith Tricks and Shortcuts
- Posts: 14 | Joined: 03-January 12
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#2
3 January 2012 - 03:29 PM
michel123456
Molecule
Entertaining blog. Well done.
Michel
- Posts: 2,899 | Joined: 28-November 09
- Reply
#3
3 January 2012 - 03:48 PM
CaptainPanic
Usually himself
It's a good blog... everybody should develop their own little tricks to calculate, and maybe this helps some people. For me, I have my own ways.
From the blog:
I find it easier to say that 195 is 5 less than 200.
200/5=40
So, 195/5 should be 39.
By now, with 4 significant numbers it depends on the work you do. For me the good-enough answer would often be "a bit less than 600", and the calculation would go something like:
2978/5 is a little less than 3000/5, which is a little less than 600.
You don't always need 4 significant numbers. But if you do, I am not sure that dividing by 5 is so much more difficult than multiplying by 2 and dividing by 10. Still, for some people this can be helpful, and you can never practice simple mental calculations too much.
From the blog:
Quote
Dividing a large number by five is actually very simple. All you do is multiply by 2 and move the decimal point to 1 digit:
a) 195 ÷ 5
Step1: 195 × 2 = 390
Step2: Move the decimal: 39.0 or just 39
a) 195 ÷ 5
Step1: 195 × 2 = 390
Step2: Move the decimal: 39.0 or just 39
I find it easier to say that 195 is 5 less than 200.
200/5=40
So, 195/5 should be 39.
Quote
b) 2978 ÷ 5
Step 1: 2978 × 2 = 5956
Step2: 595.6
Step 1: 2978 × 2 = 5956
Step2: 595.6
By now, with 4 significant numbers it depends on the work you do. For me the good-enough answer would often be "a bit less than 600", and the calculation would go something like:
2978/5 is a little less than 3000/5, which is a little less than 600.
You don't always need 4 significant numbers. But if you do, I am not sure that dividing by 5 is so much more difficult than multiplying by 2 and dividing by 10. Still, for some people this can be helpful, and you can never practice simple mental calculations too much.
This post has been edited by CaptainPanic: 3 January 2012 - 03:51 PM
Veni, vidi, modeli - I came, I saw, and I modeled it
- Posts: 3,542 | Joined: 23-January 08
- Reply
#4
3 January 2012 - 04:27 PM
Mental Math
Quark
michel123456, on 3 January 2012 - 03:29 PM, said:
Entertaining blog. Well done.
Thanks.
CaptainPanic, on 3 January 2012 - 03:48 PM, said:
It's a good blog... everybody should develop their own little tricks to calculate, and maybe this helps some people. For me, I have my own ways.
From the blog:
I find it easier to say that 195 is 5 less than 200.
200/5=40
So, 195/5 should be 39.
By now, with 4 significant numbers it depends on the work you do. For me the good-enough answer would often be "a bit less than 600", and the calculation would go something like:
2978/5 is a little less than 3000/5, which is a little less than 600.
You don't always need 4 significant numbers. But if you do, I am not sure that dividing by 5 is so much more difficult than multiplying by 2 and dividing by 10. Still, for some people this can be helpful, and you can never practice simple mental calculations too much.
From the blog:
I find it easier to say that 195 is 5 less than 200.
200/5=40
So, 195/5 should be 39.
By now, with 4 significant numbers it depends on the work you do. For me the good-enough answer would often be "a bit less than 600", and the calculation would go something like:
2978/5 is a little less than 3000/5, which is a little less than 600.
You don't always need 4 significant numbers. But if you do, I am not sure that dividing by 5 is so much more difficult than multiplying by 2 and dividing by 10. Still, for some people this can be helpful, and you can never practice simple mental calculations too much.
You are precisely right!
- Posts: 14 | Joined: 03-January 12
- Reply
#5
4 January 2012 - 08:39 PM
michel123456
- Posts: 2,899 | Joined: 28-November 09
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