Data Interpretation for Banking Prelims: The Five Calculations You Need
Most DI questions use five calculations: total, average, percentage change, ratio and share of total. Learn each with shortcuts and worked examples.
By the World MCQ Forum India Editorial Team · 27 October 2026 · 2 min read
Data interpretation (DI) sets look intimidating: a table or chart and five questions underneath. But almost every question asks for one of five calculations. If you can do these five quickly and accurately, DI becomes one of the most reliable scoring areas in the Quant section.
We’ll use one small table throughout:
| Branch | New accounts |
|---|---|
| P | 240 |
| Q | 360 |
| R | 300 |
| S | 180 |
1. Total
Add the values: 240 + 360 + 300 + 180 = 1,080.
Shortcut: add in pairs that make round numbers. 240 + 360 = 600 and 300 + 180 = 480, so the total is 1,080.
2. Average
Average = total ÷ number of items = 1,080 ÷ 4 = 270.
Shortcut: pick a base (say 300) and average the differences: −60, +60, 0, −120. The differences sum to −120, which is −30 per branch, so the average is 300 − 30 = 270.
3. Percentage change
Percentage change = (new − old) ÷ old × 100.
From P to Q: (360 − 240) ÷ 240 × 100 = 50% increase.
The trap: the base is always the starting value. From Q back to P, the change is (240 − 360) ÷ 360 × 100 = 33.33% decrease, not 50%.
4. Ratio
Highest to lowest: 360 : 180, which simplifies to 2 : 1.
Shortcut: divide both numbers by their highest common factor (here 180).
5. Share of total (percentage of the whole)
Q’s share = 360 ÷ 1,080 × 100 = 33.33%.
Shortcut: learn common fractions as percentages. 360/1,080 = 1/3 = 33.33%. Other useful values: 1/6 = 16.67%, 1/8 = 12.5%, 1/12 = 8.33%.
How to attack a DI set in the exam
- Read the title and units first. Is the table in thousands? In crores? Percentages or absolute numbers?
- Glance at all the questions before calculating. Several often need the same total; work it out once.
- Approximate when the options are far apart. If the options are 18%, 25%, 33% and 50%, rough maths is enough.
- Calculate exactly when the options are close. 33.3% versus 33.8% needs care.
- Skip a set quickly if the first question needs heavy calculation. Time spent there costs you easier marks elsewhere.
A one-week DI routine
- Days 1–2: fraction–percentage table and percentage change, 20 questions a day.
- Days 3–4: averages and ratios with the shortcuts above.
- Days 5–6: full DI sets of five questions, timed at 6 minutes each.
- Day 7: review every mistake. Did you misread the units, use the wrong base, or round too early?
Start with our data interpretation MCQs. Each solution shows the calculation, so you can check your method as well as your answer.