Logical Reasoning: Concepts & Theory

There are many types of Logical puzzles & Maths Puzzles asked in various types of Aptitude Exams. These types of questions are explained one by one.
Alphabet Series:  These types of questions are most frequently asked in Logical puzzles section of most of the management exams.
The Alphabet: The English alphabet contains 26 letters. The first half that is the first 13 letters are from A to M & the second half that is last thirteen letters are from N to Z.
EJOTY: For convenience, it is advisable to remember a simple acronym called EJOTY. With the help of this acronym, we can easily find the position of any letter in the alphabet without much effort.
E – 5th, J – 10th, O – 15th, T – 20th, Y – 25th
Now for instance, we wish to find the 12th letter from the left side. We know that O is the 10th letter. Therefore L will be the 12th letter of the alphabet.
Finding Positions: You get the questions like these much more commonly in these tests, which provides you alphabetical positions from the right side.
Let us say that there are seven boys standing in a row, ABCDEFG. If we see that C is standing on 3rd position from the left while standing 5th from the right. The sum of both the positions is 5+ 3 = 8 while total number of students is 7. So if position is given from Left side, subtract it from total number of students and then add one. This will give you the position from the right side.
Number Series:  These types of questions are also very often asked in Logical Puzzles section of Aptitude exams.
There are a few examples given of Number series:
Example 1: Find the next number in the series:
101, 102, 104, 107, 111, 116….
In the example above we can see that differences between two consecutive terms given are 1, 2, 3, 4 & 5 respectively. Therefore the next difference has to be 6. The next term therefore should be 116 + 6 = 122.
Example 2: Find the next term in the series:
1, 3, 8, 19, 42…
In this example we can see that second term is given by multiplying first term by 2 and then adding 1, third term is given by multiplying second term by 2 and then adding 2, next multiplying by 2 and then adding 3, then multiplying by 4 and then adding 4, so next term has to be 42 * 5 = 170 + 1 = 171.
Example 3: Find the next term in the series: 
4, 2, 2, 3, 6, 15, 45…
In the above example,
4*0.5 = 2
2*1= 2
2* 1.5 = 3
3*2 = 6
6* 2.5 = 15
15 * 3 = 45
Therefore next term will be 45 * 3.5 = 157.5