Q40·CSAT · Prelims 2023
Odd one out among number groups (Primes)
ReasoningClassificationSequence & pattern● Medium
Question
Choose the group which is different from the others:
Options
a
17, 37, 47, 97
b
31, 41, 53, 67
c
71, 73, 79, 83
dAnswer
83, 89, 91, 97
Explanation
Scan each group independently to analyze the mathematical prime/composite properties of the numbers listed inside them:
Group (a): 17, 37, 47, 97 \rightarrow All four are prime numbers.
Group (b): 31, 41, 53, 67 \rightarrow All four are prime numbers.
Group (c): 71, 73, 79, 83 \rightarrow All four are prime numbers.
Group (d): 83, 89, 91, 97 \rightarrow The number 91 is a composite integer: ⟨MATH⟩91 = 13 × 7⟨/MATH⟩.
Because group (d) contains a composite number while all alternate choices contain exclusively prime integers, group (d) is the odd one out.
Memorize prime values up to 100 to quickly spot common deceptive composites like 91 (13 × 7) or 57 (19 × 3) in odd-one-out tracking items.
Answer: (d).
Question details
Year
2023
Paper
CSAT
Question
Q40
Section
Logical & Analytical Reasoning
Sub-topic
Classification
Type
Sequence & pattern
Difficulty
Medium
Source hint
Pattern recognition
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