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#### Numbers Important Questions

6th Standard

Reg.No. :
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Maths

Time : 01:00:00 Hrs
Total Marks : 50
5 x 1 = 5
1. The prime factorisation of 60 is 2 $\times$ 2 $\times$ 3 $\times$ 5. Any other number which has the same prime factorisation as 60 is

(a)

30

(b)

120

(c)

90

(d)

impossible

2. If the number 6354 * 97 is divisible by 9, then the value * is

(a)

2

(b)

4

(c)

6

(d)

7

3. The number 87846 is divisible by

(a)

2 only

(b)

3 only

(c)

11 only

(d)

all of these

4. Which of the following pairs is co-prime?

(a)

51, 63

(b)

52, 91

(c)

71, 81

(d)

81, 99

5. The HCF of two numbers is 2 and their LCM is 154. If the difference between the numbers is 8, then the sum is

(a)

26

(b)

36

(c)

46

(d)

56

6. 5 x 1 = 5
7. The number of distinct prime factors of the smallest 4 digit number is ___________

()

2

8. The HCF of 45 and 75 is ___________

9. If the LCM of 3 and 9 is 9, then their HCF is _______________

10. The LCM of 26, 39 and 52 is ____________

11. The least number that should be added to 57 so that the sum is exactly divisible by 2,3, 4 and 5 is ______________

12. 5 x 1 = 5
13. The sum of any number of odd numbers is always even

(a) True
(b) False
14. Every natural number is either prime or composite

(a) True
(b) False
15. If a number is divisible by 6, then it must be divisible by 3.

(a) True
(b) False
16. 16254 is divisible by each of 2, 3, 6 and 9.

(a) True
(b) False
17. The number of distinct prime factors of 105 is 3.

(a) True
(b) False
18. 5 x 2 = 10
19. Express 42 and 100 as the sum of two consecutive primes.

20. Express 31 and 55 as the sum of any three odd primes.

21. Write the smallest and the biggest two digit prime number.

22. Write the smallest and the biggest three digit composite number.

23. The sum of any three odd natural numbers is odd. Justify this statement with an example.

24. 5 x 3 = 15
25. Find the ratio of the HCF and the LCM of the numbers 18 and 30.

26. Find the smallest number that can be divided by 254 and 508 which leaves the remainder 4.

27. What is the smallest 5 digit number that is exactly divisible by 72 and 108?

28. The LCM of two numbers is 432 and their HCF is 36. If one of the numbers is 108, then find the other number.

29. Find the length of the longest rope that can be used to measure exactly the ropes of length 1m 20cm, 3m 60cm and 4m.

30. 2 x 5 = 10
31. Find the HCF of the numbers 18, 24 and 30 by factor tree method.

32. There are four Mobile Phones in a house. At 5 a.m, all the four Mobile Phones will ring together. Thereafter, the first one rings every 15 minutes, the second one rings every 20 minutes, the third one rings every 25 minutes and the fourth one rings every 30 minutes. At what time, will the four Mobile Phones ring together again?