Q4 of 55 Page 53

Write down separately the prime and composite numbers less than 20.

Prime numbers are the numbers that has only two factors: 1 and number itself.

A composite number has more than two factors.

Prime numbers less than 20 are;

2, 3, 5, 7, 11, 13, 17 and 19.

Composite numbers less than 20 are;

4, 6, 8, 9, 10, 12, 14, 15, 16, and 18.

Note: Every Number that is not a prime number is a composite number.

State whether the following statements are True or False:

(a) The sum of three odd numbers is even.

(b) The sum of two odd numbers and one even number is even.

(d) If an even number is divided by 2, the quotient is always odd.

(e) All prime numbers are odd.

(f) Prime numbers do not have any factors.

(g) Sum of two prime numbers is always even.

(h) 2 is the only even prime number.

(i) All even numbers are composite numbers.

(j) The product of two even numbers is always even.

The numbers 13 and 31 are prime numbers. Both these numbers have same digits 1 and 3. Find such pairs of prime numbers upto 100.

What is the greatest prime number between 1 and 10?

Express the following as the sum of two odd primes:

(a) 44 (b) 36

Questions · 55

3. Playing with Numbers

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