Page 161 - New Medley 5 Semester 1

B. Write E for even and O for odd numbers in each of the following.
1. 47 2. 96 3. 104 4. 9004

5. 43253 6. 896701 7. 45388 8. 24067

9. 731015 10. 123452

C. Identify primes and composites in the following numbers.
1. 13 2. 21 3. 89 4. 65

5. 37 6. 19 7. 77 8. 69

9. 89 10. 41

D. Solve the following problems.

1. How many pairs of twin primes are there from 31 to 70?

2. Write the prime factorisation of 18, 40, 60 and 96 using the division
method.

3. Find the prime factorisation of 24, 32, 56 and 72 using the factor tree
method.

4. Write the number whose prime factorisation is first five primes.

5. (a) Can a pair of co-primes have both odd numbers?

(b) Can a pair of co-primes have both even numbers?

Justify your answer with examples.

E. State True or False for the following statements.

1. Every prime number is an odd number.

2. 1 is neither prime nor composite.

3. 7 × 9 × 11 is the prime factorisation of 691.

4. Two even numbers can be co-primes.

5. Successor of the smallest 3-digit odd number is a prime number.

HCF and LCM

Highest Common Factor (HCF)

Consider the factors of numbers 12 and 20.

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