Number System Quiz
Practice quiz on Number System (Numerical & Mental Ability). 10 exam-style questions with explanations.
About This Quiz
Number System Quiz — Questions with Solutions
All 10 questions from this quiz with the correct answer and explanation. Attempt them yourself first, then open each solution to check your reasoning.
Q1.Which of the following is a prime number?
- A.27
- B.39
- C.33
- D.29
Show answer
Answer: D. 29
29 has only two factors.
Q2.The smallest prime number is
- A.3
- B.2
- C.1
- D.0
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Answer: B. 2
2 is the smallest and only even prime.
Q3.How many prime numbers are between 1 and 20?
- A.7
- B.10
- C.8
- D.9
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Answer: C. 8
2,3,5,7,11,13,17,19.
Q4.The number 0 is
- A.Whole number but not natural
- B.Negative number
- C.Prime number
- D.Natural number
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Answer: A. Whole number but not natural
Natural numbers begin at 1.
Q5.The HCF of two co-prime numbers is
- A.1
- B.The larger number
- C.The smaller number
- D.0
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Answer: A. 1
Co-primes have no common factor except 1.
Q6.Which of these is divisible by 3?
- A.1235
- B.1237
- C.1234
- D.1233
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Answer: D. 1233
Digits of 1233 sum to 9.
Q7.The sum of first n odd numbers is
- A.2n
- B.n(n+1)
- C.n^2
- D.n^3
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Answer: C. n^2
1+3+5+...(2n-1) = n^2.
Q8.Which of the following is an irrational number?
- A.0.25
- B.4
- C.Square root of 2
- D.1/3
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Answer: C. Square root of 2
Square root of 2 is irrational.
Q9.The unit digit of 7^4 is
- A.9
- B.1
- C.7
- D.3
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Answer: B. 1
7^4 = 2401.
Q10.Which is the smallest composite number?
- A.9
- B.2
- C.4
- D.6
Show answer
Answer: C. 4
4 is the smallest composite.
Frequently Asked Questions
Is Number System Quiz free to attempt on AajExam?
Yes. Number System Quiz is completely free. You only need a free AajExam account to track your score, view detailed solutions and unlock cross-attempt analytics.
How long does it take to complete Number System Quiz?
Number System Quiz runs on a 10-minute timer in real exam-style conditions. The clock starts the moment you click Start, mirroring the time pressure of the actual exam.
Are detailed solutions provided?
Yes. Every question on Number System Quiz ships with a complete step-by-step solution, the underlying concept, and (where applicable) shortcut tricks. You can also discuss any question with the AajExam community.
Can I attempt Number System Quiz multiple times?
Yes. You can attempt this quiz as many times as you like. Each attempt is recorded separately so you can track improvement in score, accuracy and time-management.
Which government exams does this quiz prepare me for?
Number System questions appear regularly in SSC CGL, CHSL, MTS, GD; IBPS PO, Clerk; SBI PO, Clerk; RRB NTPC, Group D; UPSC prelims and most State PSC exams. The specific weightage varies by exam — check the exam pattern on the corresponding AajExam exam page for details.