math shortcuts by dashmesh academy

1
Amazing Math Trick BY DASHMESH ACADEMY

• 234X2341234-875???
• Trick! Trick!

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2
The 7-11-13 trick!
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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 7x 11x 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!

3
The 3367 trick
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• This trick is similar to the 7-11-13 trick. It's
  harder to do, but it looks far more miraculous!
• Get a friend to pick any 2 digit number e.g. 74
• x 3367
• To work out the final answer you have to imagine
  the original number written out three times e.g.
  747474 then divide it by three. 249158
• This one takes practice, but unlike the others,
  it's very hard to see how it's done!

4
The MISSING DIGIT trick!

• Here it is!
• 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.
  78341 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
• THE SECRET
• 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 78318 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 7318 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!

5
The "24" Mystery!
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• 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.
• WHY?
• If you understand algebra, (and you've read The
  Phantom X ) then you'll know that all prime
  numbers can be written as (6n1) or (6n-1).
• (6n1)2 36n12n1. So (6n1)2 -1 36n12n.
  This factories to 12n(3n1). Either n or (3n1)
  must be even, therefore the whole expression must
  be divisible by 24.
• (6n-1)2 36n-12n1. 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.

6
The Prime Number Trick

• Using prime numbers, you can amaze your friends
  with a prime prediction...
• Ask your friends to pick any prime number bigger
  than 5, but they must not tell you what it is.
• Square it. (In other words multiply the prime
  number by itself.)
• Add 17
• Divide by 12
• Without knowing which prime number your friends
  picked, you can still tell them There will be
  a remainder of 6.
• For example, if you want to try the trick with
  the prime number 2801, here's what to push
• 2801 2801 17 / 12
• ...and that's the answer! Now find a new prime
  number and try it.

7
THE AMAZING MATH TRICK OF 1999

• 1.  First of all, pick the number of days a week
  that you
•   would like to eat out.
• 2.  Multiply this number by 2.
• 3.  Add 5.
• 4.  Multiply it by 50.
• 5.  If you have already had your birthday this
  year . . .
•  add 1749.
• If you have NOT had your birthday yet this
  year . . .
• add 1748.
• 6. Last step Subtract the four digit year that
  you
• were born.
• You should now have a three digit number
• The first digit of this was your original number
  (i.e.
• how many times you want to go out to eat each
  week).
• The second two digits are your age !!!
• This is the only year it will ever work, so
  spread the
• fun around while it lasts . . .

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8
5 squared shortcutTrick 1
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• Here is a really quick way to square any number
  with a 5 on the end Lets take
•  
• Ok, so what you have to do is split up the
  numbers, giving you
• and   
• Forget about the for the moment and do this
• Always add 1, adding 1 to the 4, so we get 4 1
  5
• Then multiply this answer, 5, by the original
  first number, 4
• 5 X 4 20
• So what you have is 20 and
• Everyone knows 25 right? Well it does. This is
  what makes it easy.
• Put the two answers together and that's the
  answer!
• 2025

9
5 squared shortcutTrick 2
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• This works for any number ending in but when the
  numbers get over 100 it tends to get a little
  trickier with the multiplication.
• Give it a try with another number.
• Try , it isn't difficult.
• Split the numbers apart
• 8 and
• Again, forget about the
• Add 1 to 8 
• 8 1 9
• Multiply 9 by the first number, which was 8
• 9 X 8 72
• Now, put all the numbers together, 72 and
•   25

10
Squaring a 2-digit number beginning with 5

• Take a 2-digit number beginning with 5.
• Square the first digit.
• Add this number to the second number to find the
  first part of the answer.
• Square the second digit this is the last part of
  the answer.
•    Example
• If the number is 58, multiply 5 5 25 (square
  the first digit).
• 25 8 33 (25 plus second digit).
• The first part of the answer is 33   3 3 _ _
• 8 8 64 (square second digit).
• The last part of the answer is 64    _ _ 6 4
• So 58 58 3364.
•    See the pattern?
• For 53 53, multiply 5 5 25 (square the
  first digit).
• 25 3 28 (25 plus second digit).
• The first part of the answer is 28   2 8 _ _
• 3 3 9 (square second digit).
• The last part of the answer is 09    _ _ 0 9
• So 53 53 2809.

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11
Squaring a 2-digit number ending in 5

• Choose a 2-digit number ending in 5.
• Multiply the first digit by the next consecutive
  number.
• The product is the first two digits XX _ _.
• The last part of the answer is always 25 _ _ 2
  5.
•    Example
• If the number is 35, 3 4 12 (first digit
  times next number). 1 2 _ _
• The last part of the answer is always 25 _ _ 2
  5.
• So 35 35 1225.
•    See the pattern?
• For 65 65, 6 7 42 (first digit times next
  number) 4 2 _ _.
• The last part of the answer is always 25 _ _ 2
  5.
• So 65 65 4225.

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12
Squaring numbers made up of sixes

• Choose a a number made up of sixes.
• The square is made up of
• one fewer 4 than there are repeating 6's
• 3
• same number of 5's as 4's
• 6
•    Example
• If the number to be squared is 666
• The square of the number has  4's (one less than
  digits      in number)           4 4 3
                              3 5's (same number
  as 4's)        5 5 6                             
        6
• So 666 3666333 443556.
•    See the pattern?
• If the number to be squared is 66666
• The square of the number has  4's (one less than
  digits       in number)           4 4 4 4 3
                                  3 5's (same
  number as 4's)            5 5 5 5 6
                                            6
• So 66666 66666 4444355556.

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13
Multiply Up to 20X20 In Your Head

• 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.
• Try this
• 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!

14
The 11 Rule

• 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 (549)
• Put the resulting 9 in the hole 594. That's it!
  11 x 54594
• 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 ... 5712 ... 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 627Practice
  it on paper first!

15
Finger Math 9X Rule

• 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!

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16
Multiplication Tricks

• Multiply by 11
• 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 44 2 6. 2 5 7Last number
  5The 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

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17
Be Good

• Have Nice day with the Math trick join dashmesh
  academy for more shortcuts ph.9878043061