Core ConceptRead this first — the foundation of the topic
Line graphs are one of the most frequently tested data interpretation questions in SSC CGL. They show how data changes over time using connected points on a coordinate plane. The x-axis typically shows time periods (years, months, days) while the y-axis shows values (sales, population, temperature, etc.). Key Rules for Line Graphs:
1. Each point represents a specific value at a specific time 2. The line connecting points shows the trend between periods
5. Horizontal line = no change 6. Multiple lines can represent different categories for comparison
Formula BlockMemorise — at least one formula appears in every paper
• Percentage Change = [(New Value - Old Value) / Old Value] × 100
• Average = Sum of all values / Number of values
• Rate of Change = (Change in Value) / (Change in Time)
• Ratio = Value A : Value B
Exam PatternsWhat examiners ask — read before attempting PYQs
SSC CGL typically asks 5 questions per line graph. Common question types include: percentage increase/decrease between years, finding averages, comparing values, calculating ratios, and identifying maximum/minimum values. Questions often test your ability to read coordinates accurately and perform quick calculations.
ShortcutsUse these to save 30–60 seconds per question
#1 - Quick Percentage Change:
For small percentages, use this mental math trick: 10% = 1/10, 20% = 1/5, 25% = 1/4, 33.33% = 1/3, 50% = 1/2. This helps you estimate answers quickly without lengthy calculations.
Worked ExampleSolve this step-by-step before moving on
Answer - 40% decrease
Worked Example 2:
From the same graph, find the average sales over three years.
1
Step 1
Add all values - 40 + 50 + 30 = 120 lakhs
2
Step 2
Divide by number of years - 120 ÷ 3 = 40 lakhs
3
Step 3
Answer - Average sales = 40 lakhs
Shortcut Trick #2 - Reading Values Quickly:
Always check the scale first. If y-axis shows 'in thousands' or 'in lakhs', multiply accordingly. Mark the grid lines mentally to avoid misreading coordinates.
Shortcut Trick #3 - Estimation for Speed:
For percentage calculations, round numbers to nearest 10 or 5 for quick estimation. Then fine-tune if needed. This saves precious exam time.
The #1 Most Common Trap:
Students often misread the scale or units on axes. A graph showing 'Sales in thousands' means 5 on the graph = 5,000 actual sales. Always check what the axes represent before solving. This single mistake causes more wrong answers than calculation errors. Another trap is confusing percentage increase with percentage of total - read questions carefully to understand what exactly is being asked.
Key Points to Remember
Line graphs show data changes over time using connected points on coordinate axes
A line graph shows the monthly sales of a shop from January to June. The sales in January, February, March, April, May, and June were ₹5,000, ₹7,000, ₹6,000, ₹8,000, ₹9,000, and ₹10,000 respectively. What is the total sales for the first three months?
Practice 2easy
A line graph displays the temperature recorded at noon on each day from Monday to Friday. The temperatures were 25°C, 28°C, 26°C, 30°C, and 32°C respectively. By how many degrees did the temperature increase from Monday to Friday?
Practice 3easy
A line graph shows the number of students present in a class over 5 weeks. The attendance was 40, 38, 42, 45, and 48 students respectively. In which week was the attendance exactly 42 students?
Practice 4medium
A line graph shows the number of books sold by a shop over 5 months: January (40), February (60), March (50), April (80), May (70). What is the average number of books sold per month?
Practice 5medium
A line graph displays the temperature (in °C) recorded on different days: Monday (20), Tuesday (25), Wednesday (22), Thursday (28), Friday (26). What is the difference between the highest and lowest temperatures?
Practice 6medium
A line graph shows the distance travelled (in km) by a cyclist each week for 4 weeks: Week 1 (120), Week 2 (150), Week 3 (140), Week 4 (180). In which week was the distance maximum and what was the increase from Week 3 to Week 4?
Practice 7medium
A line graph records the number of students absent from school over 5 days: Day 1 (8), Day 2 (12), Day 3 (5), Day 4 (10), Day 5 (15). How many more students were absent on Day 5 compared to Day 3?
Practice 8hard
A line graph shows the monthly sales (in ₹ thousands) of a shop from January to June: January 40, February 55, March 50, April 65, May 75, June 80. What is the average increase in sales per month from January to June?
60-Second Revision — Line Graphs
Remember: Check axis labels and scale multipliers before solving any question
Formula: Percentage change = [(New-Old)/Old] × 100 for increase/decrease questions
Trap: Don't confuse 'in thousands' scale - 5 on graph means 5000 in reality
Speed tip: Use 10%=1/10, 25%=1/4, 50%=1/2 for quick mental calculations
Pattern: SSC asks maximum/minimum values, averages, and year-to-year comparisons
Accuracy: Read coordinates carefully by marking grid lines mentally
Strategy: Attempt easier questions first - direct reading questions before complex calculations