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Numerical Ability · AFCAT

NA11 — Data Interpretation

📊 Numerical Ability – NA11 AFCAT Level ★ High Priority

📌 AFCAT Focus 2022–2026: DI gives 2–3 questions per paper. Questions come with a graph or table, then 2–3 questions based on it. Skills tested: reading values accurately, computing percentages, finding ratios. Speed matters — practice reading graphs in under 10 seconds. No complex maths; the difficulty is in careful reading.

1. How to Approach DI Questions

Fig. 1.1 — DI Question-Solving Strategy: 4 Steps

2. Graph Types & What to Check

Fig. 2.1 — DI Graph Types: Bar, Pie, Line, Table — Key Reading Rules

💡 DI Speed Tips for AFCAT:
1. Approximate first — eliminate 2 options, then calculate precisely.
2. Pie charts: If you see 36°, it's 10% (36/360×100). If 72°, it's 20%. Memorise: 36°=10%, 18°=5%.
3. Bar graphs: Find maximum/minimum by eye before computing any ratio.
4. % change: Always use (new−old)/old, NOT (old−new)/new.

TABLE DI & MIXED DI

3. Table-Based DI — Reading & Calculating

Table DI Strategy: (1) Read column headers first. (2) Identify which row + column the question points to. (3) Check if values are in thousands/lakhs/crores — scale matters. (4) For % calculations: always use the correct base (row total or column total as specified).

Product	2020 Sales	2021 Sales	2022 Sales	Total
Product A	400	500	600	1500
Product B	300	350	450	1100
Product C	200	250	300	750
Total	900	1100	1350	3350

✎ Worked Example — Table DI (3 questions on above table)

Q1: What is the % growth in total sales from 2020 to 2022?
Q2: Product A's share in 2022 total?
Q3: Which product showed maximum % growth 2020→2022?

Q1: Growth = (1350−900)/900 × 100 = 450/900 × 100 = 50%
Q2: A in 2022 = 600/1350 × 100 = 44.4%
Q3: A: (600−400)/400×100 = 50% | B: (450−300)/300×100 = 50% | C: (300−200)/200×100 = 50% (all equal here)

✔ Q1: 50% | Q2: 44.4% | Q3: All equal at 50%

4. Mixed DI — Combining Two Data Sources

Mixed DI appears in AFCAT: You get TWO graphs/tables together — e.g., a bar graph showing total production and a pie chart showing percentage share by product. Questions require cross-referencing both sources. Strategy: (1) Read both sources before attempting questions. (2) Identify which source gives totals and which gives ratios/%. (3) Multiply total × % to get individual value.

📊 Mixed DI Example Setup

Source 1 (Bar): Total income in Year 2022 = Rs 10 lakh
Source 2 (Pie): Salary = 40%, Rent = 25%, Food = 20%, Others = 15%
Q: What is spent on rent? → Rs 10 lakh × 25% = Rs 2.5 lakh
Q: Salary − Food? → Rs 10 lakh × (40%−20%) = Rs 2 lakh

📊 Common Mixed DI Types

Table + Bar: Table gives totals, bar shows year-wise breakdown
Bar + Pie: Bar shows totals, pie shows % distribution
Line + Table: Line shows trend, table gives exact figures for calculation
Key rule: Never use data from one source to answer a question that needs the other source — read carefully which source is required

📐 Formula Sheet — NA11

Bar / Line Graph

% change = (new−old)/old × 100
Ratio of values = direct reading
Average = sum of values / count
% share = value/total × 100

Pie Chart

Angle = (value/total) × 360°
% = angle/360 × 100
Value = % × total / 100
36° = 10% | 72° = 20% | 18° = 5%

Table DI

Row total / Col total first
% of row total = cell/row × 100
Ratio: read two cells, simplify
Always check units in header

Common Calculations

Average of n values: sum/n
% increase: always on original (old)
Ratio a:b: simplify by GCD
Missing value: use given ratio/avg

📝 Topic-Wise PYQs — NA11

Q1. In a pie chart, a sector representing 'Transport' has an angle of 54°. If total expenditure = Rs 20,000, what is spent on Transport? AFCAT PYQ

(a) Rs 2,000(b) Rs 3,000(c) Rs 2,500(d) Rs 4,000

✔ Answer: (b) Rs 3,000

% = 54/360×100 = 15%. Value = 15%×20,000 = Rs 3,000.

Q2. A bar graph shows sales (units): 2019=400, 2020=500, 2021=450, 2022=600. % increase from 2019 to 2022? AFCAT PYQ

(a) 40%(b) 50%(c) 25%(d) 33%

✔ Answer: (b) 50%

% change = (600−400)/400 × 100 = 200/400 × 100 = 50%.

Q3. Average of values shown in a table — Year: 2018=80, 2019=90, 2020=70, 2021=100, 2022=60 — is: AFCAT PYQ

(a) 75(b) 80(c) 85(d) 70

✔ Answer: (b) 80

Sum = 80+90+70+100+60 = 400. Average = 400/5 = 80.

🧠 Quick Memory Chart — NA11

📊 Graph Reading

Read title & axis labels first
% change = (new−old)/old×100
% share = value/total×100
Average = sum/count

🥧 Pie Chart

Angle = (value/total)×360
36° = 10%
72° = 20%
90° = 25%

🏆 DI Strategy

Approximate → eliminate
Then calculate precisely
Use old value for % change
Check units carefully

📝 Mock Tests 🎯 Subject Quiz ✈️ Telegram

Q4. A table shows exports (in crore): Steel=240, Textiles=360, Chemicals=200. What % is Textiles of total? AFCAT PYQ

(a) 40%(b) 45%(c) 36%(d) 30%

✔ Answer: (b) 45%

Total = 240+360+200 = 800. Textiles % = 360/800 × 100 = 45%.

Q5. A line graph shows annual profit: 2019=Rs50L, 2020=Rs60L, 2021=Rs45L, 2022=Rs75L. Highest % increase from previous year was in: ⚡ Tricky

2020: (60−50)/50×100=20%. 2021: decrease (ignore). 2022: (75−45)/45×100=66.7%. 2022 has the highest % increase.

Q6. Pie chart: Education=90°, Health=72°, Defence=54°, Others=144°. Total budget=Rs 200 cr. Health budget? AFCAT PYQ

(a) Rs 30 cr(b) Rs 40 cr(c) Rs 50 cr(d) Rs 36 cr

✔ Answer: (b) Rs 40 cr

Health % = 72/360×100 = 20%. Budget = 20% of 200 = Rs 40 crore.