Technique-to-Techinical: non technical part of competitive examinations

Almost exams like up UPSC, S.S.C, PSU'S, Bank PO, Clerical, CDS, NDA, B. Ed., ETT comprise of questions from Reasoning (also known as Mental Ability or Aptitude), Aptitude, General English and general awareness.

for English refers a good book
" A MIRROR OF COMMON ERRORS" by Dr. Ashok Kumar Singh

for Math:
1. Quicker Maths, M.TYRA (for Basics)

10 ARITHMETIC TIPS

1. Quick Square

If you need to square a 2 digit number ending in 5,
Multiply the first digit by itself + 1, and put 25 on the end. That is all!
25² = (2x(2+1)) & 25
2 x 3 = 6
625

e.g.
25^2 =>2+1=3=> 2*3=6.25=625
95^2 =>9+1=10 =>9*10=>90.25=9025

remember codes
                           9801-->9
     1089-->3
                           4356-->6

e.g.
for square of 9 using above codes

9^2    is    _8_1 = 81
99^2    is 9801 = 9801
999^2 is 999001   = 998001

similarly for 3

3^2 is _0_9    = 09
33^2 is    1089 = 1089
333^2 is 110889 = 110889

similarly for 6

6^2 is    _3_6    = 36
66^2   is    4356    = 4356
666^2 is 443556 = 443556

2. multiples of 11

for large numbers:

1234*11==> 4+3=7
                      3+2=5    ^
                      2+1=3    |
        ==> 357
write the first and last digit according given number 13574

another method :
Take the original number and imagine a space between the two digits,
Now add the two numbers together and put them in the middle

its only for two digit number like 52*11 ==> 5_(5+2)_2 ==> 572

3. multiply up to 20*20 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.

4.Square 2 Digit Number: UP-DOWN Method

Square a 2 Digit Number, for this example 37:

Look for the nearest 10 boundary
In this case up 3 from 37 to 40.
Since you went UP 3 to 40 go DOWN 3 from 37 to 34.
Now mentally multiply 34x40
The way I do it is 34x10=340;
Double it mentally to 680
Double it again mentally to 1360
This 1360 is the FIRST interim answer.
37 is "3" away from the 10 boundary 40.
Square this "3" distance from 10 boundary.
3x3=9 which is the SECOND interim answer.
Add the two interim answers to get the final answer.
Answer: 1360 + 9 = 1369

With practice this can easily be done in your head.

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non technical part of competitive examinations

4.Square 2 Digit Number: UP-DOWN Method