The security personnel of a leading employment organization insisted o...
To find the largest ID number that satisfies the given conditions, we need to first understand the divisibility rules for each number from 1 to 9.
- The number should be divisible by 1: All numbers are divisible by 1.
- The number should be divisible by 2: The last digit of the number should be even.
- The number should be divisible by 3: The sum of all its digits should be divisible by 3.
- The number should be divisible by 4: The last two digits of the number should be divisible by 4.
- The number should be divisible by 5: The last digit of the number should be 0 or 5.
- The number should be divisible by 6: The number should be divisible by 2 and 3.
- The number should be divisible by 7: There is no simple rule for divisibility by 7.
- The number should be divisible by 8: The last three digits of the number should be divisible by 8.
- The number should be divisible by 9: The sum of all its digits should be divisible by 9.
To find the largest ID number, we can start with the largest digit, which is 9, and place it in the first available position.
- The first digit: Since the sum of the four digits should be divisible by 9, we can choose the largest digit that is less than or equal to 9, which is 9 itself.
- The second digit: Since the number should be divisible by 8, the last three digits should be divisible by 8. The largest three-digit number that is divisible by 8 is 992. So, the second digit is 9.
- The third digit: Since the sum of the three digits should be divisible by 3, and we have already used the digit 9, we can choose the next largest digit, which is 8.
- The fourth digit: Since the number should be divisible by 2, the last digit should be even. The largest even digit that is not used yet is 6.
So, the largest ID number that satisfies all the conditions is 99826.
The sum of the first four digits (9 + 9 + 8 + 2) is 28.
Therefore, the correct answer is option (c) 28.