23. Data interpretation: tables and charts
Free study material · concepts, shortcuts & solved questions
Read the title, unit, scale, categories and total before calculating. Percentage share=part/whole×100; percentage change=(new−old)/old×100. For a pie chart, sector angle=(value/total)×360°.
Method before formula Estimate first and compare options. A bar that looks twice as high may not represent twice the value if the scale begins above zero. In a table, avoid adding values that belong to different units or years. |
Formula and decision table
Task | Formula |
Share | part/total×100 |
Growth | (new−old)/old×100 |
Pie angle | part/total×360° |
Average | sum/count |
Worked understanding
A reliable solution has five visible moves: identify the data, choose the base or unit, write the rule, substitute carefully, and check the size of the answer. The examples in this chapter are deliberately small so that the method remains visible.
Calculation discipline Before pressing ahead, state the denominator or unit in words. For example: profit on CP, discount on MP, average over number of items, speed in metres per second, and probability over the fixed sample space. |
Solved examples from this chapter
Question focus | Correct move | Answer |
240 out of 800 is what share? | 240/800×100=30%. | C. 30% |
Value grows from 200 to 250. Increase: | 50/200×100=25%. | B. 25% |
A pie slice for 25% has angle: | 25% of 360=90°. | B. 90° |
What an examiner is testing
The options around Data interpretation: tables and charts usually represent a wrong base, a missed conversion, a sign error or a shortcut used outside its condition. Say the base and unit before calculating, estimate the result, and use substitution or a reverse operation as the final check.
Step-by-step answer construction
Example 1: 240 out of 800 is what share? First identify the requested quantity and its base or unit. Apply the chapter rule, keep the operation visible, estimate the expected range, and compare the result with the options. The correct answer is 30%, because 240/800×100=30%.
Example 2: Value grows from 200 to 250. Increase: First identify the requested quantity and its base or unit. Apply the chapter rule, keep the operation visible, estimate the expected range, and compare the result with the options. The correct answer is 25%, because 50/200×100=25%.
Example 3: A pie slice for 25% has angle: First identify the requested quantity and its base or unit. Apply the chapter rule, keep the operation visible, estimate the expected range, and compare the result with the options. The correct answer is 90°, because 25% of 360=90°.
Chapter practice
1. 240 out of 800 is what share?
(A) 20% (B) 25% (C) 30% (D) 40%
Answer: C. 30% | Explanation: 240/800×100=30%.
2. Value grows from 200 to 250. Increase:
(A) 20% (B) 25% (C) 30% (D) 50%
Answer: B. 25% | Explanation: 50/200×100=25%.
3. A pie slice for 25% has angle:
(A) 45° (B) 90° (C) 120° (D) 180°
Answer: B. 90° | Explanation: 25% of 360=90°.
SSC CGL speed and trap clinic
For Data interpretation: tables and charts, speed comes after classification. Before calculating, say aloud what the number means, what the denominator is, and what unit the answer must carry. Then use the nearest-option check to catch a sign, base or conversion error.
Checkpoint | What to verify | Typical SSC mistake |
Base | Which quantity is the base in Data interpretation: tables and charts? | Using selling price instead of cost price, or part instead of total |
Unit | Are time, distance, area and rate in compatible units? | Mixing hours with minutes or km/h with m/s |
Direction | Should the answer increase, decrease or stay bounded? | Accepting an impossible negative length or probability above 1 |
Estimate | What range should the answer lie in before exact work? | Trusting a long calculation that is far from the options |
Reverse check | Can the answer be substituted back into the condition? | Stopping at an algebraic value without verification |
Mini decision drill
1. Write the first operation you would perform in a Data interpretation: tables and charts question and why.
2. State the most dangerous denominator or unit in this chapter.
3. Give one condition under which a shortcut would be invalid.
4. Create a small numerical example and verify it by a second method.
Revision evidence Do not tick this chapter because you recognised the formula. Tick it only after you solve one direct question, one altered-condition question and one mixed-paper question correctly. |