Questions

5 Marks Questions

Take a timed test

3 questions · self-marked practice — reveal the answer and mark yourself.

Question 15 Marks
Identify whether each statement is true or false. Explain.
(a) There is no prime number whose units digit is 4.
(b) A product of primes can also be prime.
(c) Prime numbers do not have any factors.
(d) All even numbers are composite numbers.
(e) 2 is a prime and so is the next number, 3. For every other prime, the next number is composite.
Answer
(a) True.
A prime number must end in 1, 3, 7, or 9 (except for the number 2) because any number ending in 0, 2, 4, 6 or 8 is divisible by 2.
Thus, there is no prime number whose units digit is 4.
(b) False.
A product of prime numbers is only prime if it involves exactly one prime number. When you multiply two or more prime numbers together, the result is always a composite number, not a prime. As this number has 2 factors now.
(c) False.
Prime numbers have exactly two factors 1 and itself.
(d) False.
The number 2 is an even number, but it is not composite. As it is a prime number.
(e) True.
For every prime number greater than 2, the next number is composite.
View full question & answer
Question 25 Marks
Find the prime factorizations of the following numbers: 64, 104, 105, 243, 320, 141, 1728, 729, 1024, 1331, 1000.
Answer
(a) The prime factorization of 64 is 2 × 2 × 2 × 2 × 2 × 2.
(b) The prime factorization of 104 is 2 × 2 × 2 × 13.
(c ) The prime factorization of 105 is 3 × 5 × 7.
(d) The prime factorization of 243 is 3 × 3 × 3 × 3 × 3.
(e) The prime factorization of 320 is 2 × 2 × 2 × 2 × 2 × 2 × 5.
(j) The prime factorization of 141 is 3 × 47.
(g) The prime factorization of 1728 is 2 × 2 × 2 × 2 × 2 × 2 × 3 × 3 × 3.
(h) The prime factorization of 729 is 3 × 3 × 3 × 3 × 3 × 3.
(f) The prime factorization of 1024 is 2 × 2 × 2 × 2 × 2 × 2 × 2 × 2 × 2 × 2.
(j) The prime factorization of 1331 is 11 × 11 × 11.
(k) The prime factorization of 1000 is 2 × 2 × 2 × 5 × 5 × 5.
View full question & answer
Question 35 Marks
Look at the list of primes till 106. What is the smallest difference between two successive primes? What is the largest difference?
Answer
To find the smallest difference between two successive prime numbers up to 100, let’s list the prime numbers in that range and calculate the differences between each pair: Prime numbers up to 100: 2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97
Differences between successive primes:
• 3 – 2 = 1
• 5 – 3 = 2
• 7 – 5 = 2
• 11 – 7 = 4
• 13 – 11 = 2
• 17 – 13 = 4
• 19 – 17 = 2
• 23 – 19 = 4
• 29 – 23 = 6
• 31 – 29 = 2
• 37 – 31 = 6
• 41 – 37 = 4
• 43 – 41 = 2
• 47 – 43 = 4
• 53 – 47 = 6
• 59 – 53 = 6
• 61 – 59 = 2
• 67 – 61 = 6
• 71 – 67 = 4
• 73 – 71 = 2
• 79 – 73 = 6
• 83 – 79 = 4
• 89 – 83 = 6
• 97 – 89 = 8
The smallest difference between two successive primes up to 100 is 1 (between the primes 2 and 3).
The largest difference between two successive primes up to 100 is 8, which occurs between the primes 89 and 97.
View full question & answer
5 Marks Questions - MATHS STD 6 Questions - Vidyadip