Background on DI – Two-Part Analysis
The Two-Part Analysis question type in GMAT’s Data Insights (DI) section tests logical reasoning, algebraic manipulation, and critical thinking. These questions require selecting two correct answers, one for each column, from a given list of options.
They often involve:
- Mathematical relationships (equations, percentages, ratios)
- Logical reasoning (best choices based on conditions)
- Word problems (decision-making, revenue/cost analysis)
The challenge is balancing precision with speed—misinterpreting constraints or solving only part of the problem leads to errors.
Top Tips to Score High on DI – Two-Part Analysis
1. Read the Question Prompt Carefully
- Identify what both parts of the answer represent.
- Look for restrictions and relationships between the two components.
- If it’s a word problem, break it into smaller solvable parts.
2. Organise Given Information
- Convert word problems into equations or tables.
- If options include numerical values, plug them in rather than solving algebraically.
- Identify if it’s a dependency question (where one part affects the other).
3. Use the Answer Choices Smartly
- Eliminate impossible choices early.
- If a direct calculation is difficult, try plugging in the easiest values first.
- Watch out for trap answers, which include partial solutions or values from misinterpretations.
4. Prioritise Efficient Calculation
- Avoid unnecessary algebra—approximate when possible.
- Use ratios and proportions instead of long calculations.
- If applicable, use the difference or sum of the two parts as a shortcut.
5. Practise Common Question Patterns
- Linear Equations: Questions involving total cost, distance, time.
- Work & Rate Problems: Work efficiency, speed vs. time relationships.
- Profit & Revenue Analysis: Break-even calculations, cost-benefit analysis.
- Logical Selection Questions: Matching two conditions correctly.
6. Manage Time Wisely
- If stuck, use educated guessing: eliminate extreme or duplicate values.
- Don’t spend more than 2 minutes per question—move on if necessary.
- Use a process of elimination instead of solving everything manually.
Here are a few Examples to get you acquainted with these questions.
Question #01: Work and Efficiency
A and B together can complete a project in 10 days. A alone can complete the project in x days, while B alone can complete it in y days.
– The ratio of the efficiency of A to B is 3:2.
– A works for 4 days before B joins.
| Fraction of Work Done by A in 4 Days | Remaining Fraction of Work |
|---|---|
| A. \( \frac{4}{x} \) | A. \( 1 – \frac{4}{x} \) |
| B. \( \frac{4}{x} \times \frac{3}{5} \) | B. \( 1 – \frac{4}{x} \times \frac{3}{5} \) |
| C. \( \frac{4}{x} \times \frac{3}{2} \) | C. \( 1 – \frac{4}{x} \times \frac{3}{2} \) |
| D. \( \frac{4}{x} \times \frac{2}{5} \) | D. \( 1 – \frac{4}{x} \times \frac{2}{5} \) |
| E. \( \frac{4}{x} \times \frac{5}{3} \) | E. \( 1 – \frac{4}{x} \times \frac{5}{3} \) |
| F. \( \frac{4}{x} \times \frac{2}{3} \) | F. \( 1 – \frac{4}{x} \times \frac{2}{3} \) |
Solution:
– Since A’s efficiency is \( \frac{3}{5} \) of the total rate, A alone completes \( \frac{3}{5} \) of \( \frac{4}{x} \) per day.
– After 4 days, A has completed \( \frac{4}{x} \times \frac{3}{5} \) of the work.
– The remaining work is \( 1 – \frac{4}{x} \times \frac{3}{5} \).
Correct answers: B, B
Question #02: Profit Maximisation
A retailer buys a product at £20 per unit and sells it at £p per unit. He must sell at least 50 units to cover fixed costs of £200.
| Minimum Price p | Minimum Units y |
|---|---|
| A. \( \frac{200}{50} + 20 \) | A. \( \frac{500 + 200}{p – 20} \) |
| B. \( 20 + \frac{200}{50} \) | B. \( \frac{500}{p – 20} \) |
Solution:
– To break even at x = 50, we set the profit function to zero and solve for p:
\( p = 20 + \frac{200}{50} \)– To achieve £500 profit, we solve for y:
\( y = \frac{500 + 200}{p – 20} \)Correct answers: B, A
Question #03: Investment Growth
An investor places £10,000 into an account with an annual interest rate of r%, compounded n times per year.
| Effective Rate r_eff | Amount After 2 Years |
|---|---|
| A. \( \left(1 + \frac{r}{4 \times 100} \right)^4 – 1 \) | A. \( 10,000 \times \left(1 + \frac{5}{4 \times 100} \right)^{4 \times 2} \) |
Solution:
– Effective Annual Rate formula:
\( r_{eff} = \left(1 + \frac{r}{n \times 100} \right)^n – 1 \)– Future value calculation:
\( A = 10,000 \times \left(1 + \frac{5}{4 \times 100} \right)^{4 \times 2} \)Correct answers: A, A