1) METHOD Number x 2. [Just double] Examples: 43 x 2 = 86 423 x 2 = 846 352 x 2 = 704 5237 x 2 = 10474 2) METHOD Number x 4. [double twice] Examples: 43 x 4 > 86 > 172 etc. 3) METHOD Number x 5. [Halve the number, put a '0' or vice versa] Examples: 468 x 5 = 2340 467 x 5 > 4670 > 2335 4) METHOD 2 digits x 11. [Push sum of digits in between digits] Examples: 42 x 11 > 4 (4+2) 2 > 462 36 x 11 > 3(3+6)6 > 396 81 x 11 = 891 5) METHOD Any number x 11. [Start from right. Put 1st digit; Add 1st and 2nd digits, put down; Add 2nd and 3rd, put down; ...; put down last digit. In the process put down only one digit and carry anything left in the normal way] Examples: 342 x 11 > 3 (3+4) (4+2) 2 > 3762 3817 x 11 > 3(3+8)(8+1)(1+7)7 = 4198 5976 x 11 = 6(1)5(1)7(1)36 = 65736 There are methods for multiplying, squaring, finding exact roots of just any numbers as well as solving Pythagoras triangles in seconds etc. for aptitude problems (even past CAT). If this is of use and if people are interested ....
6) METHOD Number x 99. put 00 behind and sub once Examples: 25 x 99 = 2475 67 x 99 = 6633 38 x 99 = 3762
Good! Can you please give me the reference book for more knowledge on this kind of information. Thanks
