Mathematics · Quantitative Aptitude
Number Theory
438 Questions
Number theory explores the properties and relationships of integers, focusing heavily on prime and composite numbers. Key areas include identifying prime numbers, understanding co primes, and exploring mathematical conjectures like Goldbach's. These questions are a core component of quantitative aptitude sections in banking and government exams.
Prime number identificationCo prime propertiesGoldbach conjectureOdd and even numbersDivisibility rules
Number Theory Questions
B
Correct answer
Explanation
The statement is false because the number 2 is an even number and it is also a prime number. It is the only even prime number. All other even numbers are divisible by 2 and thus not prime.
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Abundant
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Irrational
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Deficient
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Prime
B
Correct answer
Explanation
Irrational numbers are defined as numbers that cannot be expressed as a ratio or fraction of two integers. Examples include pi (π), square root of 2, and e. This is the standard mathematical definition.
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Mersenne Primes
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Leibniz Primes
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fermat Primes
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Newton Primes
A
Correct answer
Explanation
Mersenne primes are prime numbers of the form $2^n - 1$. Here, $3 (2^2-1)$, $7 (2^3-1)$, $31 (2^5-1)$, and $127 (2^7-1)$ all fit this definition. Fermat primes follow a different formula ($2^{2^n}+1$).
B
Correct answer
Explanation
The statement is false because 2 is both an even number (divisible by 2) and a prime number (has exactly two factors: 1 and 2). It is the only even prime number, which is a well-known exception.
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Pseudoperfect Number
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Pluperfect Number
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Omniperfect Number
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None of the above
B
Correct answer
Explanation
A multiperfect number (or k-perfect number) is a number where the sum of all divisors is an integer multiple of the number itself. These are also known as pluperfect numbers. Pseudoperfect numbers refer to a different property (semiperfect).
B
Correct answer
Explanation
599 is a prime number because it has no divisors other than 1 and itself. Checking divisibility by primes up to sqrt(599) ≈ 24.5 (primes: 2, 3, 5, 7, 11, 13, 17, 19, 23) shows none divide 599 evenly. 899 = 29×31, 299 = 13×23, and 799 = 17×47 are all composite.
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Prime Number
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Whole Number
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Real Number
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Natural Number
B
Correct answer
Explanation
Whole numbers are the set of natural numbers plus zero {0, 1, 2, 3...}. Natural numbers typically start at 1, and prime numbers have specific divisibility rules.
D
Correct answer
Explanation
By definition, 1 is the only positive integer that is neither prime nor composite. 2, 13, and 17 are all prime numbers because they have exactly two distinct factors. 1 has only one factor.
B
Correct answer
Explanation
A prime number is defined as a natural number greater than 1 with exactly two distinct positive divisors: 1 and itself. The number 1 has only one divisor, so it is not prime. Two is the smallest prime number.
D
Correct answer
Explanation
97 is a prime number as it has no divisors other than 1 and 97. 33 is divisible by 3 and 11; 81 is divisible by 3 and 9; 93 is divisible by 3 and 31. Thus, 97 is the only prime in the list.
C
Correct answer
Explanation
A prime number has only two factors: 1 and itself. 31, 61, and 71 are prime. However, 91 is composite because $7 \times 13 = 91$. Therefore, 91 is the correct choice as it is not a prime number.
D
Correct answer
Explanation
The smallest 3-digit number is 100. Checking numbers upwards: 101 is prime. Since 101 is not listed in the options (103, 107, 109), 'None' is the correct choice. 103, 107, and 109 are primes, but they are larger than 101.
A
Correct answer
Explanation
Two is the only even prime number because all other even numbers are divisible by 2, making them composite. A prime number has exactly two factors: 1 and itself. Since any even number greater than 2 has at least three factors (1, 2, and itself), only 2 satisfies the prime number condition among even numbers.
A
Correct answer
Explanation
The first three prime numbers are 2, 3, and 5. Their sum is 2 + 3 + 5 = 10. Remember that 1 is not considered a prime number in modern mathematics. This is a fundamental concept in number theory.