Page 43 - Maths Skill - 6

Prime Time 41

Exercise 3.2

1. Which of the following statements are ‘True’ or ‘False’?

(i) 1 is the smallest prime number.
(ii) Multiple of a number is always greater than or equal to the number itself.
(iii) Sum of two odd numbers is an even number.

(iv) All odd numbers are prime.
(v) Every natural number is either prime or composite.
(vi) The product of a prime number and an even number is also a prime number.

(vii) Both 3 and 6 are factors of 15.
(viii) If two numbers are co-prime, at least one of them must be a prime number.
(ix) Two prime numbers are always co-prime.

2. Write down all the factors of each of the following.
(i) 60 (ii) 16 (iii) 144

(iv) 56 (v) 15 (vi) 36
3. Write ‘odd’ and ‘even’ for each of the following.
(i) 13 (ii) 26 (iii) 19

(iv) 38 (v) 7 (vi) 163
4. Write down first five multiples of each of the following.

(i) 9 (ii) 19 (iii) 25
(iv) 11 (v) 20 (vi) 12
5. List all prime and composite numbers between 10 and 50.

6. List all numbers less than 100 that are multiples of.
(i) 6 (ii) 15

7. Can a composite number be odd? If yes, write the smallest odd composite number.
8. Write all pairs of twin prime numbers between 40 and 80.
9. Write odd composite numbers which are less than 30.

10. Express each of the following numbers as a sum of two odd primes.
(i) 24 (ii) 44 (iii) 76 (iv) 80

11. Express each of the following numbers as a sum of three odd primes.
(i) 31 (ii) 61 (iii) 71 (iv) 35

12. Is 24 a perfect number?
13. List all prime numbers less than 100 and having 3 as the digit at its ones place.

14. Write each of the following numbers as the sum of twin primes.
(i) 8 (ii) 24 (iii) 36 (iv) 84