Order :- Order is known as sequence. For example left, right, top, bottom, ascending and descending.
Rank:- Rank is known as position in the given sequence.
In this type of questions a set of information pertaining to persons, objects or some other entities along with their qualities, which can be compared, is provided. Candidates are required to arrange the given entities in either ascending or descending order on the basis of relative quality. At first look, such questions appear to be very simple but sometimes these are made tricky by infusing intricacies and complicated data. However, one can organise the given data quickly and easily by comprehending the given information in systematic manner. Sometimes, the given information may seem to be insufficient but a cogent and coherent analysis of the same reveals useful clues and the problem turns to be very simple. You may also find some superfluous statements, which are given to confuse you. You can recognize such statements in no time if you have gained command over such types of questions.
Now consider the following examples :

Ex. A is taller than E, B is taller than D, F is taller than C, D is taller than A and E is taller than F, then who is the tallest among them?
Answer:- A > E …(i)
B > D ….(ii)
F > C …(iii)
D > A ….(iv)
E > F ….(v)
From (i) and (v)
A > E > F ….(vi)
From (iii) and (vi)
A > E > F > C ….(vii)
From (iv) and (vii)
D > A > E > F > C …(viii)
From (ii) and (viii)
B > D > A > E > F > C
Clearly, B is the tallest among them.

Ex. A, P, R, X, S and Z are sitting in a row. S and Z are in the center, and A and P are at the ends. R is sitting on the left of A. Then who is on the right of P?
(1) A (2) X (3) S (4) Z
Answer:-

Ex. Meena correctly remember that her father's birthday is after 18th May but before 22nd May. Her brother correctly remembers that their father's birthday is before 24th May but after 20th May . On which date in May was definitely their father's birthday ?
(a) 20th
(b) 19th
(c) 18th
(d) Cannot be determined
(e) None of these
Solution:- Days by Menna, 19th, 20th or 21st May.
Days by her brother, 21st , 22nd or 23rd May.
Clearly, 21st may is common in both the groups and hence it is the required day.

Ex. Raja walks slower then Raghu and Raghu walks as fast as Guru and Krishna walks faster than Guru. Who walks the fastest?
(a) Raghu
(b) Raja
(c) Krishna
(d) Both Raghu and Guru
(e) None of these
Answer:- Arrangement in descending order,
Krishna > Guru > Raghu > Raja
Hence, Krishna is the fastest from all of them.

Ex. Seema's younger brother Sohan is older than Seeta. Sweta is younger than Deepti but elder than Seema. Who is the eldest ?
(a) Seema
(b) Sweta
(c) Seeta
(d) Deepti
Answer:- According to the question, sequence is as follows
Deepti > Sweta > Seema > Sohan > Seeta
So, Deepti is the eldest.

Finding the rank of a person from one side. Value required to find the rank of a person
Total number
Rank of same person from another side

Ex- Rashmi is 14th from the right end in a row of 40 girls. What is her position from the left end ?
Solution:- given, Total girls = 40
Rashmi position from right end = 14
∴ Rashmi position from left end = Total No. - Rank from right + 1
= 40 - 14 + 1
= 27

To Finding the total number in a sequence/order. Values required to find the total numbers.
Position of a person from one end.
Position of a person from another end.

Ex- Kavi ranked 9th from the top and 38th from the bottom in a class. How many students are there in the class ?
Solution:- given, Ranked from top = 9
Ranked from bottom = 38
∴ Total students = 9 + 38 - 1
= 46

To finding the Mid Number:
Values required to find the mid number.
Position of one person from one end.
Position of another person from another end.
Total number
Case-1- When total number is more than the addition of rank from both the end.

Ex- In a row of 40 boys, A is 11th from right end and B is 23rd from left end. Then find how many boys are in between A and B?
Solution:- given, Rank of A from right end = 11
Rank of B from left end = 23
Total number of boys = 40
Number of boys between A and B = Total no. - (Position of one person from one end + Position of another person from another end)
= 40 - ( 11 + 23 )
= 40 - 34 = 6

Case-2- When total number is less than the addition of rank from both the end. ( Overlap Case )

Ex- In a row of 25 girls, A is 15th from left end and B is 18th from right end. Then find how many girls are in between A and B ?
Solution:- given Total number = 25
Rank of A from left end = 15
Rank of B from right end = 18
Number of girls between A and B = ( Position of one person from one end + Position of another person from another end ) - ( Total number + 2 )
= ( 15 + 18 ) - ( 25 + 2 )
= 33 - 27 = 6

Examples

Ex- In a row of boys, Rajan is 10th from the right and suraj is 10th from the left. When Rajan and Suraj interchange their positions, Suraj will be 27th from the left. Which of the following will be Rajan's position from the right?
(a) 10th (b) 26th (c) 29th
(d) 25th (e) None of these
Solution:- Total number of boys = (10 + 27 - 1)
= 37 - 1 = 36
So, Rajan's position from the right
= (36 - 10) + 1 = 26 + 1 = 27
Option (e)

Ex- If each of the digits in the number 92581473 are arranged in ascending order, what will be the difference between the digits, which are fourth from the right and third from the left in the new arrangement?
(a) One (b) Two (c) Three
(d) Four (e) None of these
Solution:- After arranging in ascending order, we get
12345789
Digit fourth from the right = 5
Digit third from the left = 3
Difference = 5 - 3 = 2
Option (b)