Data Interpretation: Line Charts
CSAT · Data Interpretation
Introduction
Data interpretation (line charts) questions give you data and ask for quick, accurate calculations. They need no outside knowledge, so they are reliable marks once the reading and arithmetic are disciplined.
Key concepts
What a line shows
A line chart shows change over time. The slope between two points shows the change: a steeper upward line is a bigger increase in absolute terms.
Two or more lines
The vertical gap between lines is the difference between the series at that time; where lines cross, the values are equal.
Typical questions
| Question | Approach |
|---|---|
| Largest rise/fall | compare consecutive differences |
| Percentage growth | (later − earlier)/earlier |
| Months where one series exceeds the other | count line positions |
| Average | add the points |
| Share of combined total | value/(sum of series) |
Absolute versus percentage
A rise from 100 to 150 (+50, +50%) is smaller in absolute terms than one from 300 to 380 (+80, +26.7%) but larger in percentage terms. Read the question for which one is asked.
- % change = (new − old)/old × 100
- Share = part/total × 100
- Average = sum/count
- Pie angle = % × 3.6
Solved examples
Data set: Monthly sales
| Month | P | Q |
|---|---|---|
| Jan | 260 | 350 |
| Feb | 210 | 330 |
| Mar | 150 | 320 |
| Apr | 300 | 400 |
| May | 210 | 150 |
| Jun | 330 | 400 |
Example 1
In which month did sales of P rise the most (in units) over the previous month?
(a) Apr (b) Feb (c) Mar (d) May
- Month-on-month change for P: Feb -50, Mar -60, Apr +150, May -90, Jun +120.
- Largest rise: Apr.
Answer: (a) Apr
Example 2
What is the difference between total sales of P and Q over the six months?
(a) 540 (b) 460 (c) 1460 (d) 490
- Total P = 1460; total Q = 1950.
- Difference = 490.
Answer: (d) 490
Example 3
In Feb, what share of the combined sales came from P?
(a) 61.11% (b) 38.89% (c) 63.64% (d) 43.89%
- 210 ÷ (210 + 330) × 100 = 38.89%.
Answer: (b) 38.89%
Example 4
In how many months were the sales of P higher than those of Q?
(a) 1 (b) 0 (c) 3 (d) 2
- Compare month by month: Jan Q, Feb Q, Mar Q, Apr Q, May P, Jun Q.
Answer: (a) 1
Example 5
What were the average monthly sales of Q?
(a) 390 (b) 335 (c) 325 (d) 243.33
- Total Q = 1950; ÷ 6 = 325.
Answer: (c) 325
Data set: Monthly sales
| Month | P | Q |
|---|---|---|
| Jan | 300 | 290 |
| Feb | 400 | 320 |
| Mar | 110 | 150 |
| Apr | 370 | 160 |
| May | 120 | 260 |
| Jun | 120 | 110 |
Example 6
In which month did sales of P rise the most (in units) over the previous month?
(a) Mar (b) May (c) Apr (d) Feb
- Month-on-month change for P: Feb +100, Mar -290, Apr +260, May -250, Jun +0.
- Largest rise: Apr.
Answer: (c) Apr
Example 7
What is the difference between total sales of P and Q over the six months?
(a) 1420 (b) 130 (c) 100 (d) 180
- Total P = 1420; total Q = 1290.
- Difference = 130.
Answer: (b) 130
Example 8
In Jan, what share of the combined sales came from P?
(a) 103.45% (b) 55.85% (c) 49.15% (d) 50.85%
- 300 ÷ (300 + 290) × 100 = 50.85%.
Answer: (d) 50.85%
Example 9
In how many months were the sales of P higher than those of Q?
(a) 4 (b) 0 (c) 2 (d) 1
- Compare month by month: Jan P, Feb P, Mar Q, Apr P, May Q, Jun P.
Answer: (a) 4
Example 10
What were the average monthly sales of Q?
(a) 215 (b) 258 (c) 236.67 (d) 225
- Total Q = 1290; ÷ 6 = 215.
Answer: (a) 215
Data set: Monthly sales
| Month | P | Q |
|---|---|---|
| Jan | 360 | 160 |
| Feb | 270 | 190 |
| Mar | 130 | 210 |
| Apr | 400 | 130 |
| May | 160 | 400 |
| Jun | 100 | 150 |
Example 11
In which month did sales of P rise the most (in units) over the previous month?
(a) May (b) Mar (c) Apr (d) Feb
- Month-on-month change for P: Feb -90, Mar -140, Apr +270, May -240, Jun -60.
- Largest rise: Apr.
Answer: (c) Apr
Example 12
What is the difference between total sales of P and Q over the six months?
(a) 180 (b) 1420 (c) 150 (d) 230
- Total P = 1420; total Q = 1240.
- Difference = 180.
Answer: (a) 180
Example 13
In Apr, what share of the combined sales came from P?
(a) 80.47% (b) 75.47% (c) 24.53% (d) 307.69%
- 400 ÷ (400 + 130) × 100 = 75.47%.
Answer: (b) 75.47%
Example 14
In how many months were the sales of P higher than those of Q?
(a) 2 (b) 1 (c) 0 (d) 3
- Compare month by month: Jan P, Feb P, Mar Q, Apr P, May Q, Jun Q.
Answer: (d) 3
Example 15
What were the average monthly sales of Q?
(a) 206.67 (b) 216.67 (c) 248 (d) 236.67
- Total Q = 1240; ÷ 6 = 206.67.
Answer: (a) 206.67
- Read all questions on a set before calculating – reuse totals.
- Approximate when options are far apart; compute exactly when they are close.
- Write intermediate numbers in a mini-table.
- Using the wrong base for percentage change.
- Ignoring units (thousands, crore, %).
- Confusing absolute and percentage changes.
Practice set
Use the chart or table for each set; about 90 seconds per question.
Practice data: Monthly sales
| Month | P | Q |
|---|---|---|
| Jan | 210 | 380 |
| Feb | 280 | 270 |
| Mar | 120 | 100 |
| Apr | 170 | 360 |
| May | 380 | 370 |
| Jun | 310 | 400 |
Q1. In which month did sales of P rise the most (in units) over the previous month?
(a) Apr (b) Mar (c) Feb (d) May
Q2. What is the difference between total sales of P and Q over the six months?
(a) 410 (b) 380 (c) 1470 (d) 460
Q3. In May, what share of the combined sales came from P?
(a) 49.33% (b) 50.67% (c) 102.7% (d) 55.67%
Q4. In how many months were the sales of P higher than those of Q?
(a) 3 (b) 2 (c) 1 (d) 0
Q5. What were the average monthly sales of Q?
(a) 323.33 (b) 245 (c) 313.33 (d) 376
Practice data: Monthly sales
| Month | P | Q |
|---|---|---|
| Jan | 300 | 340 |
| Feb | 310 | 330 |
| Mar | 330 | 200 |
| Apr | 100 | 230 |
| May | 110 | 120 |
| Jun | 310 | 100 |
Q6. In which month did sales of P rise the most (in units) over the previous month?
(a) Mar (b) Jun (c) Feb (d) Apr
Q7. What is the difference between total sales of P and Q over the six months?
(a) 140 (b) 1460 (c) 110 (d) 190
Q8. In Apr, what share of the combined sales came from P?
(a) 30.3% (b) 35.3% (c) 69.7% (d) 43.48%
Q9. In how many months were the sales of P higher than those of Q?
(a) 1 (b) 0 (c) 2 (d) 3
Q10. What were the average monthly sales of Q?
(a) 243.33 (b) 230 (c) 264 (d) 220
Q1 – (d) May. Month-on-month change for P: Feb +70, Mar -160, Apr +50, May +210, Jun -70. Largest rise: May.
Q2 – (a) 410. Total P = 1470; total Q = 1880. Difference = 410.
Q3 – (b) 50.67%. 380 ÷ (380 + 370) × 100 = 50.67%.
Q4 – (a) 3. Compare month by month: Jan Q, Feb P, Mar P, Apr Q, May P, Jun Q.
Q5 – (c) 313.33. Total Q = 1880; ÷ 6 = 313.33.
Q6 – (b) Jun. Month-on-month change for P: Feb +10, Mar +20, Apr -230, May +10, Jun +200. Largest rise: Jun.
Q7 – (a) 140. Total P = 1460; total Q = 1320. Difference = 140.
Q8 – (a) 30.3%. 100 ÷ (100 + 230) × 100 = 30.3%.
Q9 – (c) 2. Compare month by month: Jan Q, Feb Q, Mar P, Apr Q, May Q, Jun P.
Q10 – (d) 220. Total Q = 1320; ÷ 6 = 220.
- Units and base first
- % change on the old value
- Reuse totals
- Approximate wisely
