Numbers Worksheet-6

Numbers Worksheet-6

1. The least number which when decreased by 7 is exactly divisible by 12, 16, 18, 21 and 28 is

(a) 1012              (b) 1008             (c) 1015              (d) 1022

2. The greatest number of 4–digits exactly divisible by 12, 15, 20 and 35 is

(a) 9999             (b) 9660            (c) 9832             (d) 9860

3. The smallest number of 4-digits exactly divisible by 12, 15, 20 and 35 is

(a) 1000             (b) 1160              (c) 1260             (d) None

4. Four bells ring at intervals of 6, 7, 8 and 9 seconds respectively. All the bells ring together after.......... seconds.

(a) 504               (b) 516                (c) 508               (d) 512

5. The greatest number that will divide 37, 50, 123 leaving remainder 1, 2 and 3 respectively is

(a) 9                    (b) 10                  (c) 15                   (d) 12

6. The greatest number that will divide 137, 182 and 422 leaving a remainder of 2 in each case is

(a) 15                  (b) 12                  (c) 21                  (d) None

7. The HCF of two number is 28 and their LCM is 336. If one number is 112 then the other number is

(a) 64                  (b) 84                 (c) 34                  (d) None

8. Prime factors of 143 are

(a) 2 × 11 × 13                               (b) 11 × 13

(c) 2 × 3 × 7                                   (d) None

9. A prime number is ...........

(a) an even number                     (b) an odd number

(c) a composite number             (d) None of these

10. If the HCF of two numbers is 1, then they are called

(a) co-primes                                (b) composite numbers

(c) prime numbers                       (d) twin primes

11. Least prime number is

(a) 1                     (b) 0                    (c) 2                    (d) 3

12. Which of the following statement is true?

(a) 1 is the smallest prime number

(b) Every prime number is an odd number

(c) The sum of two prime numbers is always a prime number

(d) None of these

13. The number 3, 116, 365 is divisible by

(a) 5                    (b) 7                    (c) 5 & 7             (d) None

14. Which of the following number is divisible by 11?

(a) 3, 116, 365                               (b) 901, 351

(c) 8,790, 322                               (d) None

15. Which of the following statement is false?

(a) If a number is divisible by 8, it must be divisible by 4.

(b) If a number is divisible by both 9 and 10, it must be divisible by 90

(c) The sum of two consecutive odd numbers is always divisible by 4

(d) None of these

16. Which of the following are prime numbers?

(a) 137                (b) 143                (c) 396               (d) 137 & 143

17. The HCF of 136, 170 and 255 is

(a) 13                  (b) 15                  (c) 17                   (d) 1

18. Which of the following pairs are co-prime?

(a) 348 & 296                                (b) 59 & 97

(c) 3025 & 4920                           (d) None

19. A prime number

(a) has exactly one factor           (b) has exactly two factors

(c) is not divisible by 2                (d) is an odd number

20. How many prime numbers are there between 10 and 30?

(a) 6                    (b) 5                    (c) 7                    (d) 8

Answer Key:

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