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This trick makes you look like your brain is a mega fast calculator!
Ask a friend to write down ANY three digit number such as 231 or 884. Ask them to multiply the number by
x 7 x 11 x 13
...but even if your friend has used a calculator, you will have written down the answer ages ago! It's fiendish!
THE SECRET: all you do is write out the starting number twice! So 231 will become 231231 and 884 will become 884884. You don't believe it? Well try it on this calculator and see for yourself! You work this calculator by clicking the mouse on the buttons. Go on, put in ANY three digit number then x7 x11 x 13 and see what you get!
Go and hide in a cupboard, or cover your eyes in some way so that you can't see what your friend is writing.
Ask a friend to secretly write down ANY number (at least four digits long). e.g. 78341
Ask the friend to add up the digits... e.g. 7+8+3+4+1 = 23
... and then subtract the answer from the first number. e.g. 78341 - 23 = 78318
Your friend then crosses out ONE digit from the answer. (It can be any digit except a zero) e.g. 7x318
Your friend then reads out what digits are left .e.g. 7-3-1-8
Even though you haven't seen any numbers, you can say what the missing digit is! EIGHT
This great trick relies on the power of 9.
After your friend has added up the digits and subtracted them, the answer will ALWAYS divide by 9. If a number divides by nine, then when you add the digits up, they will also divide by 9. If you check our example 7+8+3+1+8 = 27 which does divide by nine.
When your friend crosses a digit out, he then reads out the digits that are left. You add them up. In the example we had 7+3+1+8 = 19
All you do now is see what you have to add on to your answer to get the next number that divides by nine! The next number to divide by 9 after 19 is 27. So you need to add on EIGHT. This is the number that was crossed out!
1. Add 18 to your birth month
2. Multiply by 25
3. Subtract 333
4. Multiply by 8
5. Subtract 554
6. Divide by 2
7. Add your birth date
8. Multiply by 5
9. Add 692
10. Multiply by 20
11. Add only the last two digits of your birth year
12. Subtract 32940 to get your birthday!
The answer's format is: month/day/year. For example, an answer of 123199 means that you were born on December 31, 1999. If the answer is not right, you followed the directions incorrectly or lied about your birthday.
A Murderous Math fan called OBAID pointed out that if you square ANY prime number bigger then 3, then subtract 1, the answer always divides by 24! E.g. 112 = 121 then 121 - 1 = 120 and yes 120 does divide by 24.
If you understand algebra, (and you've read The Phantom X ) then you'll know that all prime numbers can be written as (6n+1) or (6n-1).
(6n+1)2 = 36n+12n+1. So (6n+1)2 -1 = 36n+12n. This factories to 12n(3n+1). Either n or (3n+1) must be even, therefore the whole expression must be divisible by 24.
(6n-1)2 = 36n-12n+1. So (6n-1)2 -1 = 36n-12n. This factories to 12n(3n-1). Either n or (3n-1) must be even, therefore the whole expression must be divisible by 24.
Here is a math trick so unbelievable that it will stump you. Personally I would like to know who came up with this and why that person is not running the country. 1. Grab a calculator. (you won't be able to do this one in your head) 2. Key in the first three digits of your phone number (NOT the area code) 3. Multiply by 80 4. Add 1 5. Multiply by 250 6. Add the last 4 digits of your phone number 7. Add the last 4 digits of your phone number again. 8. Subtract 250 9. Divide number by 2 Do you recognize the answer ??????
Your Age by Sex Math. This is pretty neat! Check it out.... YOUR AGE BY SEX MATH DON'T CHEAT BY SCROLLING DOWN FIRST! It takes less than a minute....... Work this out as you read... You might need a small piece of scrap paper for simple addition and subtraction. 1. First of all, pick the number of times a week that you would like to have sex. (more than once but less than 10)
2. Multiply this number by 2 (Just to be bold)
3. Add 5. (for Sunday)
4. Multiply it by 50 I'll wait while you get the calculator................
5. If you have already had your birthday this year add 1755....
If you haven't, add 1754 ....
6. Now subtract the four digit year that you were born.
You should have a three digit number
The first digit of this was your original number (i.e., how many times you want to have sex each week).
In just FIVE minutes you should learn to quickly multiply up to 20x20 in your head. With this trick, you will be able to multiply any two numbers from 11 to 19 in your head quickly, without the use of a calculator. I will assume that you know your multiplication table reasonably well up to 10x10.
Take 15 x 13 for an example.
Always place the larger number of the two on top in your mind.
Then draw the shape of Africa mentally so it covers the 15 and the 3 from the 13 below. Those covered numbers are all you need.
First add 15 + 3 = 18
Add a zero behind it (multiply by 10) to get 180.
Multiply the covered lower 3 x the single digit above it the "5" (3x5= 15)
Add 180 + 15 = 195.
That is It! Wasn't that easy? Practice it on paper first!
You likely all know the 10 rule (to multiply by 10, just add a 0 behind the number) but do you know the 11 rule? It is as easy! You should be able to do this one in you head for any two digit number. Practice it on paper first! To multiply any two digit number by 11:
For this example we will use 54.
Separate the two digits in you mind (5__4).
Notice the hole between them!
Add the 5 and the 4 together (5+4=9)
Put the resulting 9 in the hole 594. That's it! 11 x 54=594
The only thing tricky to remember is that if the result of the addition is greater than 9, you only put the "ones" digit in the hole and carry the "tens" digit from the addition. For example 11 x 57 ... 5__7 ... 5+7=12 ... put the 2 in the hole and add the 1 from the 12 to the 5 in to get 6 for a result of 627 ... 11 x 57 = 627 Practice it on paper first!
To multiply by 9,try this: (1) Spread your two hands out and place them on a desk or table in front of you. (2) To multiply by 3, fold down the 3rd finger from the left. To multiply by 4, it would be the 4th finger and so on. (3) the answer is 27 ... READ it from the two fingers on the left of the folded down finger and the 7 fingers on the right of it. This works for anything up to 9x10!
The eleven times table has always been very easy to learn up to 9 x 11. Here's a simple way of multiplying large numbers by 11 too. Let's try.
Write down the first digit. Add the first and second digits. Write it. Add the second and third digits. Write it. Again and again do this. Write down the last digit.
Example 1 - 425 x 11
First number = 4 4 + 2 = 6. 2 + 5 = 7 Last number = 5 The answer is 4675.
Example 2 - 5890 x 11
First number = 5. 5 + 8 = 13. Now we can't write 13. So, add 1 into 5. Then write down 3. 8 + 9 = 17. Again add 1 into 3. Now it is 4. After that write down 7. 9 + 0 = 9. Then write down last digit. It is 0. Answer : 64790