Page 194 - New Medley 4 Semester 1

EXERCISE 5.4

A. Categorise the following numbers as odd and even numbers.

1. 6 2. 7 3. 20 4. 36

5. 81 6. 104 7. 420 8. 501

9. 666 10. 1099 11. 7325 12. 6948

B. Identify the following as prime and composite numbers.

1. 3 2. 6 3. 7 4. 15

5. 16 6. 23 7. 31 8. 34

9. 41 10. 48 11. 53 12. 93

C. 1. Write all the prime numbers below 25.
2. Write the smallest composite number which is odd.

3. Give two examples of twin primes.

4. Is 1 a prime number or composite number?

5. Give three examples of co-primes.

6. Is the greatest two-digit number even?

7. Write the smallest composite number.

8. Are all the prime numbers odd?

9. Are 13 and 15 twin primes?

Divisibility Tests

A number is said to be divisible by the numbers that divide it completely,
i.e., without leaving a remainder. But, to check whether a number is
divisible by other number, we perform actual division and see whether
the remainder is zero or not. It is very time-consuming process. Here are

given some facts for divisibility tests that make our task easier.

Divisibility by 10

A number is divisible by 10 if its ones digit is 0. For example, 40, 50, 120,

260, etc., are divisible by 10.

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