SSC CGL 2024 Tier-I · 25 September 2024, Shift 3 · General Intelligence and Reasoning · Question 20 of 100

Text as printed on a candidate's response sheet for this shift; answer per SSC's tentative key as marked on that sheet. Solution last reviewed 10 September 2026.

Where this paper and its answers come from

SSC does not publish CGL question papers or a public answer key. The questions and options here are reproduced as printed on a candidate's own response sheet for this shift — the Commission's text, unchanged. Each answer is SSC's tentative key as marked on that sheet; SSC allowed challenges to it and never publishes a final key. The solutions are written by UnlockIAS.

Study the given diagram carefully and answer the question that follows. The numbers in different sections indicate the number of students who like to study different subjects. What is the difference between the number of students who like to study all the three subjects and that of students who like to study biology only?

(a)16
(b)3
(c)17
(d)19

Answer

Why

Correct — A. Identify the two regions the question names, then subtract.

All three subjects is the central region, the one common to Biology, Physics and Chemistry: 4.

Biology only is the crescent of the Biology circle that overlaps neither other circle: 20.

20 − 4 = 16, which is option (a).

Why the others are wrong

(b)
3 — Option (b) subtracts the wrong pair. 3 is not the gap between the all-three region and Biology only — it is the gap between the Biology-Chemistry region (8) and the Biology-Physics region (5).
(c)
17 — 17 is the Biology overlap total. 5 + 8 + 4 = 17 counts every Biology student who also takes another subject, which is not the difference option (c) is being offered for.
(d)
19 — 19 is the three pairwise regions added up. 5 + 8 + 6 = 19 counts the students taking exactly two subjects, which option (d) offers in place of the difference asked for.

Concept

A three-circle Venn item is read region by region, and the wording maps onto exactly one region or one simple combination of them.

Only is the word doing the work. "Biology only" means the crescent overlapping nothing — 20 — not the whole Biology circle, which would be 20 + 5 + 8 + 4 = 37.

"All the three subjects" is always the single central region, 4. Once both regions are named the arithmetic is trivial, and that is deliberate: the item tests reading, not calculation.

The circles are labelled by arrows from outside rather than by names placed inside them, so check which circle each arrow points at before assigning any number. Biology is top left, Physics top right, Chemistry bottom.

Key facts

The figure prints Biology only as 20, Physics only as 38 and Chemistry only as 42.
The pairwise-only regions are Biology-Physics 5, Biology-Chemistry 8 and Physics-Chemistry 6.
The central all-three region is 4, so the difference asked for is 20 − 4 = 16.

Study next

The vocabulary of Venn questions: only, both, at least one, exactly two, all threeReading a three-circle diagram when the question wants a sum across regions rather than one regionConverting a three-circle diagram into a seven-region table before reading the question

Common traps

Reading Biology only as the whole Biology circle, 37 instead of 20.
Answering with a region total instead of the difference the question actually asks for.
Assigning a number to the wrong circle because the labels sit outside the diagram on arrows.

The stem is fixed wording, and what varies is the labelling and the combination asked for.

24 Sep 2024, 16:00, Reasoning Q.20 wants the difference between the all-three region of a persons-who-can-drive diagram and everyone who drives any two vehicles, which is the three pairwise regions added together.

19 Sep 2024, 16:00, Reasoning Q.18 wants two subjects but NOT the third.

Reasoning Q.25 of this sitting runs the same diagram type on modes of transport.

Related PYQs

No directly related past PYQ was found.