Which of the following statements are true?(a)  If a number is divisible by 3, it must be divisible by 9.(b) If a 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)  If two numbers are co-primes, at least one of them must be prime.(f)  All numbers which are divisible by 4 must also be divisible by 8.g)  All numbers which are divisible by 8 must also be divisible by 4.(h)  If a number exactly divides two numbers separately, it must exactly divide their sum.(i)  If a number exactly divides the sum of two numbers, it must exactly divide the two numbers    separately.

Explanation

To determine which of the statements are true, we will analyze each statement one by one.

### Step-by-Step Solution:

1. **Statement (a)**: If a number is divisible by 3, it must be divisible by 9.
- **Analysis**: A counterexample is the number 6. It is divisible by 3 (6 ÷ 3 = 2) but not divisible by 9 (6 ÷ 9 = 0.67).
- **Conclusion**: **False**

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