Selvam is on 9th position from upwards and on 38th position from downwards in a class. How many students are in class?
46
Understanding Ranking Questions: Finding Total Students
This question asks us to find the total number of students in a class based on a student's position from both the top and the bottom of the rank list. These types of problems are common in reasoning sections of competitive exams and test our understanding of order and ranking concepts.
Let's analyze the information given:
- Selvam's position from the top (upwards) is 9th.
- Selvam's position from the bottom (downwards) is 38th.
We need to determine the total number of students in the class.
Logic for Solving Ranking Problems
When we are given the rank of one person from both ends of a row or list, we can find the total number of people using a simple formula. Think about it this way: when we count Selvam from the top, he is the 9th student. When we count him from the bottom, he is the 38th student. In this process of adding the ranks from both ends, Selvam has been counted twice.
To find the total number of distinct students, we need to add the two given ranks and then subtract 1 (to correct for counting the person twice).
The formula is:
Total number of students = (Position from Top) + (Position from Bottom) - 1
Step-by-Step Calculation to Find Total Students
Let's apply the formula using the given information:
- Position from Top = 9
- Position from Bottom = 38
Total students = \(9 + 38 - 1\)
First, add the two positions:
\(9 + 38 = 47\)
Now, subtract 1 to correct for double counting Selvam:
\(47 - 1 = 46\)
So, there are 46 students in the class.
Total Students in the Class: The Answer
Based on the calculation, if Selvam is 9th from the top and 38th from the bottom, the total number of students in the class is 46.
Let's verify the logic. If there are 46 students and Selvam is 9th from the top, it means there are \(46 - 9 = 37\) students below him. If he is 38th from the bottom, it means there are \(38 - 1 = 37\) students below him. This confirms our total count.
Revision Table: Key Ranking Formulas
| Scenario | Formula for Total People |
|---|---|
| Rank of one person from both ends is known | Total = (Rank from Left/Top) + (Rank from Right/Bottom) - 1 |
| Total people and rank from one end is known (finding rank from other end) | Rank from Other End = Total - Rank from One End + 1 |
Additional Information on Order and Ranking
Order and Ranking questions involve arranging people or items based on certain parameters like height, weight, marks, or position in a row. The key is to correctly interpret the positions and avoid double-counting or missing anyone.
- Understanding "between": If a question asks about the number of people "between" two people, do not include those two people in the count.
- Overlapping: Sometimes, the ranks might overlap, especially in questions involving two different people's positions and the number of people between them. These require careful calculation to determine maximum or minimum possible people.
- Relative Ranking: Some questions might give relative positions (e.g., A is 5 places to the left of B). Visualizing the arrangement or using diagrams can be very helpful for these.
Mastering the basic formula and understanding how ranks relate to the total number of items is fundamental to solving these types of ranking questions.
Important Questions from Rank Based
All 32 students in a class are standing in a row facing north. Akash is 12th from the right end while Priya is 18th from the left end. How many people are standing between Akash and Priya?
In a class of 36 students, the number of boys are twice the number of girls. In the class, there are 13 boys before Reema (girl) whose position is 19th in the class. How many girls are there in the class after Reema?
In a row of 21 children facing North, Nitin is third to the right of Sita who is ninth from the right end of the row. What is Nitin's position from the left end?
Six students, Abhay, Bhanu, Charu, David, Ekta and Farheen, are the top six rank holders in a school. The rank of Bhanu is between the ranks of Charu and David. Bhanu is on the fourth rank. There are two students between the ranks of Ekta and David. Ekta is at the lowest rank among all the given students. The rank of Abhay is immediately below the rank of Farheen. Who is on the fifth rank?
In a row of 35 students, Ramesh is at the 24th position from the beginning. The last two students left. What is Ramesh's position from the end of the row?
