Question

EXERCISE 3.54
Which of the following statements are true?
(a) If a number is divisible by 3, it must be divisible by 9.
(b) Ifa number is divisible by 9, it must be divisible by 3.
(c) A number is divisible by 18, if it is divisible by both 3 and 6.
(d) If a number is divisible by 9 and 10 both, then it must be divisible by 90.
(e) Iftwo numbers are co-primes, at least one of them must be prime.
( All numbers which are divisible by 4 must also be divisible by 8.​

Answer 1

Answer:

(a) False  Ex - 12

(b) True ex- Any multiple of 9 :-  18 , 27

(c)True   Ex - Any multiple of 18 :-  18,36,72

(d) True - This is because if a number is divisible by two given co-prime                      numbers then it is also divisible by their product.

(e) False  ex- 9 and 10

(f)  False ex- 12

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