📊 Tables – A Quick Guide for the Delhi Forest Guard Exam
(Quantitative Aptitude – Tables)
1️⃣ Simple Explanation
A table is a systematic arrangement of data in rows and columns that makes it easier to read, compare, and analyze information.
In quantitative aptitude, tables help you:
- Organise data (frequency, percentages, conditional relationships).
- Find patterns (sums, totals, averages).
- Solve problems that require quick extraction of specific information.
2️⃣ Key Points to Remember
| # | Concept | Why It Matters | Quick Tip |
|---|---|---|---|
| 1 | Types of Tables | • Frequency tables (counts) • Percentages tables • Contingency tables (cross‑tabulation) • Cumulative frequency tables |
Know which type helps in which kind of question. |
| 2 | Row vs Column | Rows identify the category (e.g., age group), columns identify the variable (e.g., number of cases). | Label clearly to avoid confusion. |
| 3 | Totals & Subtotals | Needed for percentages, averages, and to check consistency. | Always compute the grand total first. |
| 4 | Percentages | Percentage = (Part/Whole) × 100. Often you’ll have a whole in the table (e.g., total population). |
Use the “part” cell and the grand total. |
| 5 | Cumulative Frequency | Adds up frequencies up to that row (useful for median, percentiles). | Read from left to right, adding each frequency. |
| 6 | Data Extraction | Locate the row/column that matches the question’s criteria. | Use the header labels to pinpoint the cell. |
| 7 | Missing Data | Often a table will have a “?”. Use the given totals or relationships to solve. | Set up an equation Row total = Sum of row entries. |
| 8 | Diagonal / Symmetry | In some contingency tables, the diagonal may represent “same condition” counts. | Helpful in probability problems. |
| 9 | Remember Units | Units (kg, km, % etc.) matter for interpretation. | Keep track of units when computing derived values. |
| 10 | Check for Consistency | Verify that all totals match given totals; if not, double‑check calculations. | Quick sanity check: all subtotals + totals = grand total. |
3️⃣ Worked Example
Problem
A forest department records the number of wildlife sightings per month for the first six months of the year. The data are given below.
| Month | Sighting Count |
|---|---|
| Jan | 24 |
| Feb | 31 |
| Mar | 27 |
| Apr | 35 |
| May | 30 |
| Jun | ? |
Questions
a) Find the number of sightings in June.
b) What percentage of the total sightings were made in the first three months?
c) Calculate the average (mean) sightings per month for the six months.
Solution
Step 1 – Build the Frequency Table
| Month | Sightings |
|---|---|
| Jan | 24 |
| Feb | 31 |
| Mar | 27 |
| Apr | 35 |
| May | 30 |
| Jun | ? |
| Total | ? |
Step 2 – Find the Missing Value (June)
The problem often provides the total or a relationship.
Assume the total sightings for the six months are 180 (given elsewhere in the exam).
Compute:
Total = 24 + 31 + 27 + 35 + 30 + June
180 = 147 + June
June = 180 – 147 = 33
| Month | Sightings |
|---|---|
| Jan | 24 |
| Feb | 31 |
| Mar | 27 |
| Apr | 35 |
| May | 30 |
| Jun | 33 |
| Total | 180 |
Step 3 – Percentage of First Three Months
Sum of Jan–Mar = 24 + 31 + 27 = 82
Percentage = (82 / 180) × 100 ≈ 45.56%
Answer a) 33 sightings in June.
Answer b) ≈ 45.6 % of total sightings.
Step 4 – Mean Sightings
Mean = Total / 6 = 180 / 6 = 30
Answer c) 30 sightings per month on average.
4️⃣ Quick Revision Summary
| Topic | What to Know | Quick Check |
|---|---|---|
| Table Types | Frequency, Percentages, Contingency, Cumulative | Identify by header |
| Totals | Grand total, Row/Column totals | Sum rows → grand total |
| Percentages | Part/Whole × 100 | Use whole = grand total |
| Missing Cells | Use given totals or equations | Row total = sum of entries |
| Mean | Sum of all values ÷ number of entries | Check with totals |
| Median / Percentiles | Use cumulative frequency | Locate the middle‑value row |
| Cross‑Tab | Two categorical variables | Look for diagonal (matching) counts |
| Units | Keep consistent | Convert if needed |
Tip: Before doing any calculation, draw the table on paper. A visual layout reduces errors and speeds up data extraction.
Final Thought 🚀
Tables are the backbone of many quantitative aptitude problems. Mastering how to read, fill, and manipulate them turns seemingly complex data into simple arithmetic. Practice with different table types, and always double‑check totals and percentages. Good luck with your preparation!