Numbers Worksheet-7

Numbers Worksheet-7

1. The sum of the prime numbers between 90 and 100 is

(a) 188               (b) 281               (c) 376                (d) 97

2. Which of the following numbers is a perfect number?

(a) 6                    (b) 28                 (c) Both              (d) None

3. By Goldbach's conjecture, every even number greater than 4 can be expressed as a sum of

(a) two even numbers                 (b) two odd prime numbers

(c) two composite numbers       (d) two co-prime numbers

4. What least value should be given to * so that the number 653*47 is divisible by 11?

(a) 9                    (b) 6                    (c) 2                    (d) 1

5. The least number of 4 digits which is exactly divisible by 13 is

(a) 1052             (b) 1039             (c) 1032             (d) 1001

6. The greatest number which when divides 258 and 323 leaving remainders 2 and 3 respectively is

(a) 32                  (b) 64                 (c) 16                  (d) 128

7. The HCF and LCM of two numbers is 16 and 192 respectively. If one of the numbers is 64, the other one is

(a) 48                 (b) 24                 (c) 72                  (d) none

8. The smallest number which when divided by 4, 6, 10, 15 gives the same remainder 3 is

(a) 57                  (b) 123                (c) 63                  (d) 39

9. A number is always divisible by 90 if

(a) it is divisible by both 2 and 45

(b) it is divisible by both 5 and 18

(c) it is divisible by both 9 and 10     

(d) All of these

10. The LCM of two numbers is 3718. Which of the following numbers cannot be possibly the HCF of these numbers?

(a) 13                  (b) 26                 (c) 104                (d) 143

11. The prime factors of 24 are

(a) 2 × 3 × 4                                   (b) 2 × 2 × 2 × 3

(c) 6 × 4                                          (d) 8 × 3

12. The number 10 has four factors: 1, 2, 5 and 10. The table below lists the number of factors for some numbers.

From this we can say that the number of prime numbers between 20 and 30 is

(a) 0                    (b) 2                    (c) 3                    (d) 4

13. Find a number which is a multiple of all the numbers from 1 to 10?

(a) 5040             (b) 1260             (c) 720               (d) 1440

14. Observer the following sums. Then find the sum of 1 + 3 + 5 + 7 + 9 + ..... + 19?

(a) 121                (b) 81                  (c) 100                (d) 64

15. The number 24 has ______

(a) 2 factors      (b) 4 factors      (c) 6 factors      (d) 8 factors

16. A prime number has _____

(a) 0, 2, 4, 6 or 8 at one's place

(b) 1, 3, 5, 7 or 9 at one's place

(c) 2 factors only

(d) 2 multiplies only

17. Write the least 2-digit number that has 2, 5 and 8 as factors?

(a) 80                 (b) 40                 (c) 16                  (d) 10

18. Observe the given multiples of 37.

37 × 3 = 111

37 × 6 = 222

37 × 9 = 333

37 × 12 = 444

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Find the product of 37 × 27 ?

(a) 999

(b) Greatest 3 digit number

(c) Either 999 or  Greatest 3 digit number

(d) Smallest 3-digit number

19. The factor of the number shown on the spike abacus is:

(a) 8                    (b) 7                    (c) 5                    (d) 9

20. Ramu wrote two digits of a 3–digit number on the blackboard as shown below:

Find the missing digit if it has 11 and 13 as factors?

(a) 2                    (b) 4                    (c) 6                    (d) 8

Answer Key:

(1)-(d); (2)-(c); (3)-(b); (4)-(d); (5)-(d); (6)-(b); (7)-(a); (8)-(c); (9)-(d); (10)-(c); (11)-(b); (12)-(b); (13)-(a); (14)-(c); (15)-(d); (16)-(c); (17)-(b); (18)-(c); (19)-(d); (20)-(b)