Awesome Tricks2Make Any Calculation in Seconds

Trick 1

Use the formula ALL FROM 9 AND THE LAST FROM 10 to perform instant subtractions.

• For example 1000 - 357 = 643We simply take each figure in 357 from 9 and the last figure from 10.
  
  
  So the answer is 1000 - 357 = 643
  And thats all there is to it!
  This always works for subtractions from numbers consisting of a 1 followed by noughts: 100; 1000; 10,000 etc.
  
  
• Similarly 10,000 - 1049 = 8951
  
  
• For 1000 - 83, in which we have more zeros than figures in the numbers being subtracted, we simply suppose 83 is 083.So 1000 - 83 becomes 1000 - 083 = 917
  
  
  
  Trick 2
  
  
  Here's how to use VERTICALLY AND CROSSWISE for multiplying numbers close to 100.
  • Suppose you want to multiply 88 by 98.
    Both 88 and 98 are close to 100.88 is 12 below 100 and 98 is 2 below 100.
    You can imagine the sum set out like this:
    

    
    
    As before the 86 comes from subtracting crosswise: 88 - 2 = 86
    (or 98 - 12 = 86: you can subtract either way, you will always get the same answer).
    And the 24 in the answer is just 12 x 2: you multiply vertically.
    So 88 x 98 = 8624
  This is so easy it is just mental arithmetic.
  

  Trick 3

  A quick way to square numbers that end in 5 using the formula BY ONE MORE THAN THE ONE BEFORE.
  • 75² = 562575² means 75 x 75.
    The answer is in two parts: 56 and 25.
    The last part is always 25.
    The first part is the first number, 7, multiplied by the number "one more", which is 8:
    so 7 x 8 = 56
    
  • Similarly 85² = 7225 because 8 x 9 = 72.
  
  
  Method for multiplying numbers where the first figures are the same and the last figures add up to 10.

  • 32 x 38 = 1216
  Both numbers here start with 3 and the last figures (2 and 8) add up to 10. So we just multiply 3 by 4 (the next number up) to get 12 for the first part of the answer. And we multiply the last figures: 2 x 8 = 16 to get the last part of the answer. Diagrammatically:
  • And 81 x 89 = 7209
  We put 09 since we need two figures as in all the other examples.

  
  

  Trick 4

  An elegant way of multiplying numbers using a simple pattern.

  • 21 x 23 = 483
  This is normally called long multiplication but actually the answer can be written straight down using the VERTICALLY AND CROSSWISE formula. We first put, or imagine, 23 below 21:

  

  There are 3 steps:

   a) Multiply vertically on the left: 2 x 2 = 4. This gives the first figure of the answer.

   b) Multiply crosswise and add: 2 x 3 + 1 x 2 = 8  This gives the middle figure.

   c) Multiply vertically on the right: 1 x 3 = 3  This gives the last figure of the answer.

  And thats all there is to it.
  
  
  

  • Similarly 61 x 31 = 1891

  

  • 6 x 3 = 18; 6 x 1 + 1 x 3 = 9; 1 x 1 = 1

  
  

  
  

  
  

  Trick 5

  Multiplying a number by 11.

  To multiply any 2-figure number by 11 we just put the total of the two figures between the 2 figures.
  • 26 x 11 = 286Notice that the outer figures in 286 are the 26
    being multiplied.
    And the middle figure is just 2 and 6 added up.
  • So 72 x 11 = 792

  77 x 11 = 847
  

  This involves a carry figure because 7 + 7 = 14
  we get 77 x 11 = 7₁47 = 847.

  
  

  234 x 11 = 2574

  We put the 2 and the 4 at the ends.
  We add the first pair 2 + 3 = 5.
  and we add the last pair: 3 + 4 = 7.

  
  

  
  
  Trick 6

  Method for diving by 9.

  • 23 / 9 = 2 remainder 5The first figure of 23 is 2, and this is the answer.
    The remainder is just 2 and 3 added up!
  • 43 / 9 = 4 remainder 7
    The first figure 4 is the answer and 4 + 3 = 7 is the remainder - could it be easier
    
    
    
    
    
    -->>134 / 9 = 14 remainder 8
    The answer consists of 1,4 and 8.
    1 is just the first figure of 134.
    4 is the total of the first two figures 1+ 3 = 4,
    and 8 is the total of all three figures 1+ 3 + 4 = 8.
    
    
    -->> 842 / 9 = 812 remainder 14 = 92 remainder 14
    Actually a remainder of 9 or more is not usually permitted because we are trying to find how
    many 9's there are in 842.Since the remainder, 14 has one more 9 with 5 left over the final answer will be 93 remainder 5