Question

Which one of the following number is completely divisible by 45?

• A. 181566
• B. 331145
• C. 242865
• D. 2023550

Hint:

To test divisibility by 45, simply check divisibility by 5 and 9 separately.

Answer 1

The Correct Option is C

Concept: A number is divisible by 45 if it is divisible by both 5 and 9. \[ 45 = 5 \times 9 \] Rules:
• Divisible by 5 $\Rightarrow$ last digit must be 0 or 5.
• Divisible by 9 $\Rightarrow$ sum of digits must be divisible by 9. Checking Option (C): \[ 242865 \] Last digit = 5 Therefore, divisible by 5. Sum of digits: \[ 2+4+2+8+6+5=27 \] Since \[ 27 \div 9 = 3 \] the number is divisible by 9. Hence, \[ 242865 \] is divisible by both 5 and 9. Therefore, it is divisible by 45. \[ {242865} \] Hence, Option (C) is correct.