In this guide
Ranking questions ask about positions: in a row, a queue, a class list or a line of people sorted by height. They look like arithmetic, but the arithmetic is tiny. The real skill is not counting the same person twice, and not missing one.
Ranking comes up regularly in the SSC GD reasoning section. Three formulas cover almost every row question, and one habit, writing a chain, covers the comparison questions.
The three formulas
| What you want | Formula |
|---|---|
| Total people in the row | Position from left + position from right − 1 |
| Position from the other end | Total − known position + 1 |
| People between two persons (both counted from the same end) | Larger position − smaller position − 1 |
Why the "− 1" in the first formula? The person you are counting from both sides is included in both numbers. Subtract one so they are counted once.
Why the "+ 1" in the second? If you are 1st from the left in a row of 10, you are 10th from the right, and 10 − 1 + 1 = 10. Try it on a small row whenever you doubt a formula.
Solved examples
Example 1 (total). In a row, a candidate is 7th from the left and 10th from the right. How many people are in the row?
- Total = 7 + 10 − 1.
- Answer: 16.
Example 2 (other end). In a row of 25 people, a candidate is 8th from the left. What is their position from the right?
- Position from right = 25 − 8 + 1.
- Answer: 18th.
Example 3 (between, from different ends). In a row of 30, A is 8th from the left and B is 12th from the right. How many people are between A and B?
- Bring both to the same end. B from the left = 30 − 12 + 1 = 19th.
- Between = 19 − 8 − 1 = 10.
- Check: A at 8, B at 19. The people between sit at 9 to 18, which is 10 places.
Example 4 (swapped places). In a row, A is 10th from the left and B is 15th from the right. They swap places, and A is now 18th from the left. How many people are in the row?
- After the swap, A stands where B stood. So B's old place is 18th from the left.
- That same place is 15th from the right.
- Total = 18 + 15 − 1 = 32.
Example 5 (comparison chain). A is taller than B. C is shorter than B. D is taller than A. E is shorter than C. Who is in the middle?
- Write the chain, tallest on the left: D > A > B > C > E.
- There are five people, so the middle is the 3rd.
- Answer: B.
Example 6 (class with failures). Among the students who passed, a student is 12th from the top and 29th from the bottom. 5 students failed and 3 were absent. How many students are in the class?
- Passed students = 12 + 29 − 1 = 40.
- Add those who failed and those who were absent: 40 + 5 + 3.
- Answer: 48.
Comparison questions
For "taller, heavier, older, richer" questions, turn every sentence into a piece of a chain and join the pieces.
- "A is taller than B" becomes A > B.
- "C is shorter than B" becomes B > C. Rewrite "shorter" so the chain always runs in one direction.
- Join: A > B > C.
If a sentence does not connect to the chain, keep it aside until a later sentence links it in. If two people cannot be placed relative to each other, the answer to "who is taller" between them is "cannot be determined". Do not guess.
Common mistakes
| Mistake | Correct way |
|---|---|
| Total = left + right, with no "− 1" | The person is counted twice; subtract 1 |
| Using positions from different ends in the "between" formula | Convert one position so both are from the same end |
| Subtracting 1 in "queue of 9 in front plus 6 behind" questions | If 6 people are behind the 9th, the total is 9 + 6 = 15; nobody is counted twice |
| Writing "shorter" as a separate chain | Flip it so all links point the same way |
| Forgetting failed or absent students | Ranks count only those listed; add the rest at the end |
Practice set
- A candidate is 12th from the front and 15th from the back of a queue. How many people are in the queue?
- In a row of 30, a candidate is 11th from the right. What is their position from the left?
- In a class of 50, a student ranks 20th from the top. What is the rank from the bottom?
- P is heavier than Q. R is lighter than Q. S is heavier than P. Who is the lightest?
- In a row of 15, X is 4th from the left and Y is 10th from the left. How many people are between them?
- In a row of 40, A is 10th from the left and B is 15th from the right. How many people are between them?
- M is older than N. O is younger than N. P is older than M. Q is younger than O. Who is in the middle by age?
- In a queue, a candidate is 9th from the front, and there are 6 people behind them. How many people are in the queue?
Answers:
- 26. 12 + 15 − 1.
- 20th. 30 − 11 + 1.
- 31st. 50 − 20 + 1.
- R. Chain: S > P > Q > R.
- 5. 10 − 4 − 1.
- 15. B from the left = 40 − 15 + 1 = 26th; between = 26 − 10 − 1 = 15.
- N. Chain: P > M > N > O > Q, and N is 3rd of 5.
- 15. 9 people up to and including the candidate, plus 6 behind.
What to do next
- Learn the three formulas, and test each on a row of five people drawn on paper.
- Solve 15 ranking questions a day for a week, half of them comparison chains.
- For "between" questions, always convert both positions to the same end first.
- Pair this with directions and blood relations in week three of the reasoning plan.
A note on dates and numbers. Exam patterns, vacancies and schedules change from year to year. Always confirm the current details in the latest notification on the Staff Selection Commission website .
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