Number System Quiz
Practice quiz on Number System (Mathematics). 5 real exam questions.
About This Quiz
Number System Quiz — Questions with Solutions
All 25 questions from this quiz with the correct answer and explanation. Attempt them yourself first, then open each solution to check your reasoning.
Q1.Find the missing number: 9, 18, 36, 72, ?
- A.100
- B.120
- C.144
- D.160
Show answer
Answer: C. 144
Each term ×2 → 72×2 = 144
Q2.Which is prime?
- A.21
- B.51
- C.31
- D.49
Show answer
Answer: C. 31
31 is prime.
Q3.Missing number: 14, 28, 20, 40, 32, ?
- A.64
- B.48
- C.56
- D.52
Show answer
Answer: A. 64
×2 then -8.
Q4.A number is multiplied by 7 to get 56. What is the number?
- A.6
- B.7
- C.8
- D.9
Show answer
Answer: C. 8
56 ÷ 7 = 8
Q5.How many prime numbers lie between 10 and 30?
- A.5
- B.6
- C.7
- D.8
Show answer
Answer: B. 6
Primes are 11, 13, 17, 19, 23, 29 ⇒ 6 primes.
Q6.Which of the following is a prime number?
- A.15
- B.17
- C.21
- D.27
Show answer
Answer: B. 17
17 has no divisors other than 1 and itself.
Q7.The smallest prime number is:
- A.0
- B.1
- C.2
- D.3
Show answer
Answer: C. 2
2 is the smallest and only even prime number.
Q8.The HCF of 12 and 18 is:
- A.4
- B.6
- C.8
- D.12
Show answer
Answer: B. 6
The highest common factor of 12 and 18 is 6.
Q9.The LCM of 4 and 6 is:
- A.8
- B.10
- C.12
- D.24
Show answer
Answer: C. 12
The least common multiple of 4 and 6 is 12.
Q10.Which of the following is a rational number?
- A.Square root of 2
- B.Pi
- C.3/4
- D.Square root of 3
Show answer
Answer: C. 3/4
3/4 can be expressed as a ratio of integers, making it rational.
Q11.The sum of the first 5 natural numbers is:
- A.10
- B.15
- C.20
- D.25
Show answer
Answer: B. 15
1+2+3+4+5 = 15.
Q12.Which of the following is a perfect square?
- A.45
- B.49
- C.52
- D.55
Show answer
Answer: B. 49
49 = 7 squared.
Q13.The place value of 5 in the number 3456 is:
- A.5
- B.50
- C.500
- D.5000
Show answer
Answer: B. 50
The digit 5 is in the tens place, so its place value is 50.
Q14.An even number is always divisible by:
- A.2
- B.3
- C.4
- D.5
Show answer
Answer: A. 2
By definition, every even number is divisible by 2.
Q15.Which of these is an irrational number?
- A.4
- B.Square root of 2
- C.9
- D.1/2
Show answer
Answer: B. Square root of 2
Square root of 2 cannot be expressed as a simple fraction.
Q16.The product of two negative numbers is always:
- A.Positive
- B.Negative
- C.Zero
- D.Undefined
Show answer
Answer: A. Positive
Multiplying two negative numbers gives a positive result.
Q17.The smallest 3-digit number is:
- A.99
- B.100
- C.101
- D.999
Show answer
Answer: B. 100
100 is the smallest three-digit number.
Q18.The number 0 is classified as:
- A.A natural number
- B.A whole number
- C.A prime number
- D.A negative number
Show answer
Answer: B. A whole number
0 is a whole number but not a natural number in most conventions.
Q19.Which of the following is a composite number?
- A.7
- B.11
- C.13
- D.15
Show answer
Answer: D. 15
15 = 3 x 5, so it has factors besides 1 and itself.
Q20.The reciprocal of 5 is:
- A.5
- B.1/5
- C.-5
- D.0
Show answer
Answer: B. 1/5
The reciprocal of a number n is 1/n.
Q21.Which of the following numbers is divisible by 3?
- A.25
- B.26
- C.27
- D.28
Show answer
Answer: C. 27
27's digit sum is 9, which is divisible by 3.
Q22.The value of 2 to the power 3 is:
- A.6
- B.8
- C.9
- D.16
Show answer
Answer: B. 8
2 cubed = 2x2x2 = 8.
Q23.Which of these is NOT a natural number?
- A.1
- B.2
- C.0
- D.5
Show answer
Answer: C. 0
0 is excluded from the set of natural numbers in most definitions.
Q24.The square root of 144 is:
- A.10
- B.11
- C.12
- D.14
Show answer
Answer: C. 12
12 x 12 = 144.
Q25.The sum of two odd numbers is always:
- A.Odd
- B.Even
- C.Prime
- D.Zero
Show answer
Answer: B. Even
Adding two odd numbers always results in an even number.
Frequently Asked Questions
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How long does it take to complete Number System Quiz?
Number System Quiz runs on a 25-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.