Data Interpretation: Caselets
CSAT · Data Interpretation
Introduction
Data interpretation (caselets) 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 caselet is
A caselet presents data in a paragraph instead of a chart: a school, a village survey, an office or a budget. The skill is to convert the text into a small table before answering.
Method
- Read the whole paragraph once.
- Identify the groups (girls/boys, departments, households) and the attributes (plays a sport, has LPG).
- Build a table: rows = groups, columns = attributes, with totals.
- Fill every cell you can by direct calculation; use totals to find the rest.
Percentages of percentages
'40% of the girls play' is 40% of the number of girls, not of all students. Convert to numbers early.
Fractions of the remainder
'One-third work in Accounts; of the rest, half work in Sales' – half of the remaining two-thirds, i.e. one-third of the total.
Turning words into a table
A caselet gives data in a paragraph. Before answering, convert it into a small table or tree: total → groups → subgroups. For example, 'of 1,000 students 40% are girls; 25% of girls and 10% of boys play a sport' becomes girls 400 (100 play), boys 600 (60 play).
Percentages of percentages
'30% of the remaining' means 30% of what is left after the first group is removed, not 30% of the total. Write the base of each percentage explicitly.
Overlaps
When two characteristics overlap (electricity and LPG), use a two-way table or a Venn diagram. The four cells must add up to the total.
Checking answers
After answering, verify that the groups add up to the total. A wrong base is the commonest error and usually produces an answer among the distractors.
- % change = (new − old)/old × 100
- Share = part/total × 100
- Average = sum/count
- Pie angle = % × 3.6
Solved examples
Data set: Caselet
A village has 600 households. 60% have electricity. Among households with electricity, 25% also use LPG for cooking; no household without electricity uses LPG.
Example 1
How many households use LPG?
(a) 90 (b) 150 (c) 270 (d) 100
- Electrified = 60% × 600 = 360.
- LPG users = 25% × 360 = 90.
Answer: (a) 90
Example 2
How many households have electricity but no LPG?
(a) 240 (b) 360 (c) 270 (d) 90
- 360 − 90 = 270.
Answer: (c) 270
Example 3
What percentage of all households use LPG?
(a) 21% (b) 15% (c) 60% (d) 25%
- 90 ÷ 600 × 100 = 15%.
Answer: (b) 15%
Data set: Caselet
A school has 1500 students, of whom 40% are girls. 20% of the girls and 30% of the boys play a sport.
Example 4
How many students play a sport?
(a) 390 (b) 375 (c) 330 (d) 120
- Girls = 600, boys = 900.
- Girls who play = 20% × 600 = 120; boys = 30% × 900 = 270.
- Total = 390.
Answer: (a) 390
Example 5
What percentage of all students do not play a sport?
(a) 26% (b) 75% (c) 74% (d) 79%
- Non-players = 1500 − 390 = 1110; ÷ 1500 × 100 = 74%.
Answer: (c) 74%
Example 6
Of the students who play a sport, what fraction are girls?
(a) 2/5 (b) 4/13 (c) 2/25 (d) 9/13
- 120 of the 390 players are girls = 4/13.
Answer: (b) 4/13
Data set: Caselet
A village has 800 households. 70% have electricity. Among households with electricity, 40% also use LPG for cooking; no household without electricity uses LPG.
Example 7
How many households use LPG?
(a) 224 (b) 234 (c) 320 (d) 336
- Electrified = 70% × 800 = 560.
- LPG users = 40% × 560 = 224.
Answer: (a) 224
Example 8
How many households have electricity but no LPG?
(a) 224 (b) 240 (c) 336 (d) 560
- 560 − 224 = 336.
Answer: (c) 336
Example 9
What percentage of all households use LPG?
(a) 34% (b) 28% (c) 70% (d) 40%
- 224 ÷ 800 × 100 = 28%.
Answer: (b) 28%
Data set: Caselet
An office has 180 employees in three departments. 1/5 of them work in Accounts. Of the rest, 3/4 work in Sales and the others in HR.
Example 10
How many employees work in HR?
(a) 36 (b) 40 (c) 46 (d) 108
- Accounts = 1/5 × 180 = 36.
- Rest = 144; Sales = 3/4 × 144 = 108.
- HR = 144 − 108 = 36.
Answer: (a) 36
Example 11
What is the ratio Accounts : Sales : HR?
(a) 3 : 1 : 1 (b) 1 : 3 : 1 (c) 1 : 2 : 3 (d) 36 : 108 : 37
- 36 : 108 : 36, divide by 36.
Answer: (b) 1 : 3 : 1
Example 12
What percentage of employees work in Sales?
(a) 65% (b) 75% (c) 60% (d) 20%
- 108 ÷ 180 × 100 = 60%.
Answer: (c) 60%
- 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.
- Fractions such as 1/4 or 2/5 of a total that is a multiple of 20 or 40 usually give whole numbers – if you get a decimal head-count, recheck the base.
- When several questions use the same caselet, build the full table once and answer all of them from it; this saves time and keeps the numbers consistent across questions.
- 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: Caselet
An office has 150 employees in three departments. 1/5 of them work in Accounts. Of the rest, 1/3 work in Sales and the others in HR.
Q1. How many employees work in HR?
(a) 80 (b) 90 (c) 30 (d) 40
Q2. What is the ratio Accounts : Sales : HR?
(a) 8 : 4 : 3 (b) 30 : 40 : 81 (c) 3 : 4 : 8 (d) 4 : 3 : 8
Q3. What percentage of employees work in Sales?
(a) 53.33% (b) 26.67% (c) 33.33% (d) 31.67%
Practice data: Caselet
A village has 800 households. 80% have electricity. Among households with electricity, 40% also use LPG for cooking; no household without electricity uses LPG.
Q4. How many households use LPG?
(a) 384 (b) 320 (c) 256 (d) 266
Q5. How many households have electricity but no LPG?
(a) 384 (b) 160 (c) 640 (d) 256
Q6. What percentage of all households use LPG?
(a) 40% (b) 32% (c) 80% (d) 38%
Practice data: Caselet
A village has 500 households. 70% have electricity. Among households with electricity, 40% also use LPG for cooking; no household without electricity uses LPG.
Q7. How many households use LPG?
(a) 150 (b) 210 (c) 140 (d) 200
Q8. How many households have electricity but no LPG?
(a) 210 (b) 350 (c) 150 (d) 140
Q9. What percentage of all households use LPG?
(a) 34% (b) 28% (c) 70% (d) 40%
Q1 – (a) 80. Accounts = 1/5 × 150 = 30. Rest = 120; Sales = 1/3 × 120 = 40. HR = 120 − 40 = 80.
Q2 – (c) 3 : 4 : 8. 30 : 40 : 80, divide by 10.
Q3 – (b) 26.67%. 40 ÷ 150 × 100 = 26.67%.
Q4 – (c) 256. Electrified = 80% × 800 = 640. LPG users = 40% × 640 = 256.
Q5 – (a) 384. 640 − 256 = 384.
Q6 – (b) 32%. 256 ÷ 800 × 100 = 32%.
Q7 – (c) 140. Electrified = 70% × 500 = 350. LPG users = 40% × 350 = 140.
Q8 – (a) 210. 350 − 140 = 210.
Q9 – (b) 28%. 140 ÷ 500 × 100 = 28%.
- Units and base first
- % change on the old value
- Reuse totals
- Approximate wisely
