Exercise 7B
Question 1
Fill in the blanks.
(i) ___ is a factor of all natural numbers.
(ii) Every multiple of a number is greater than or equal to the __
(iii) The smallest prime number is ___ which is the only ___ prime number.
(iv) The seven consecutive composite numbers less than 100 , so that there is no prime number between them are ___
(v) Two numbers having only 1 as a common factor are called ___ numbers.
Question 2
Answer ' T ' for True or ' F ' for False.
(i) The number of multiples of a given number are finite.
(ii) Any two consecutive numbers are co-prime.
(iii) 1 is the smallest odd prime number.
(iv) Sum of two consecutive odd numbers is always divisible by 4 .
(v) The pair of number (31,33) is an example of twin primes.
Question 3
Write the factors of
(i) 14
(ii) 36
(iii) 41
(iv) 80
(v) 97
Question 4
Write the first five multiples of each of the following.
(i) 8
(ii) 17
(iii) 24
(iv) 30
(v) 100
5. (i) Determine whether 36 is a factor of 44,496
(ii) Without actual division show that 32 is a factor of 32032
6. Tell whether each number is prime $(P)$ or composite $(C)$.
(i) 5
(ii) 31
(iii) 42
(iv) 51
(v) 63
(vi) 67
(vii) 73
(viii) 85
(ix) 91
(x) 97
7. Express:
(i) 24 and 64 each as the sum of two primes.
(ii) 31 and 65 each as the sum of three odd primes.
(iii) 14 and 95 each as the product of two primes.
8. Write
(i) All prime numbers between 50 and 80 .
(ii) The largest 2-digit composite number.
(iii) Pairs of twin primes between 1 and 50 .
Multiple Choice Questions (MCQs)
Tick (✔) the correct option.
9. The sum of the factors of 20 is
(a) 22
(b) 21
(c) 42
(d) 50
10. 72 is not a multiple of
(a) 8
(b) 12
(c) 18
(d) 16
11. Which of the following is not a prime number?
(a) 11
(b) 21
(c) 31
(d) 41
12. Which of the following is a pair of twin primes as well as co-primes?
(a) 15,17
(b) 63,65
(c) 29,31
(d) 43,45
13. Sum of the number of primes between 16 to 80 and 90 to 100 is
(a) 20
(b) 18
(c) 17
(d) 16
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