Question Details

Consider all 3-digit numbers (without repetition of digits) obtained using three non-zero digits which are multiples of 3. Let S be their sum.


Which of the following is/are correct?

1. S is always divisible by 74.

2. S is always divisible by 9.

Select the correct answer using the code given below:

Options

A

1 only

B

2 only

C

Both 1 and 2

D

Neither 1 nor 2

Show Answer

Correct Answer :

Option C

Both 1 and 2

Solution :

The correct answer is Both 1 and 2.


Step 1: Identify the eligible digits

The question specifies non-zero digits that are multiples of 3.
The single-digit non-zero multiples of 3 are 3, 6, and 9.
Since we need to form 3-digit numbers using three non-zero digits (without repetition of digits), the three digits used must be 3, 6, and 9.


Step 2: Form all possible 3-digit numbers

Using the digits 3, 6, and 9 without repetition, we can form the following 3-digit numbers:

369, 396, 639, 693, 936, and 963.


Step 3: Calculate the sum S

Let us find the sum S of all these numbers:

S = 369 + 396 + 639 + 693 + 936 + 963

Summing them up step-by-step:

369 + 396 = 765

765 + 639 = 1404

1404 + 693 = 2097

2097 + 936 = 3033

3033 + 963 = 3996

So, the sum S = 3996.


General Algebraic Approach:
For any three digits a, b, and c, the sum of all 6 possible 3-digit permutations is given by:

S = 222 × ( a + b + c )

Here, a = 3, b = 6, c = 9.

a + b + c = 3 + 6 + 9 = 18

S = 222 × 18 = 3996


Step 4: Test Statement 1 (Divisibility by 74)

Let us check if 3996 is divisible by 74:

3996 74 = 54

Since 3996 divided by 74 gives an exact integer quotient of 54, S is divisible by 74.
Thus, Statement 1 is correct.


Step 5: Test Statement 2 (Divisibility by 9)

Let us check if 3996 is divisible by 9:
Sum of the digits of 3996 is 3 + 9 + 9 + 6 = 27, which is a multiple of 9.

3996 9 = 444

Since 3996 divided by 9 gives an exact integer quotient of 444, S is divisible by 9.
Thus, Statement 2 is also correct.


Conclusion:

Both statements 1 and 2 are correct. Hence, the correct code option is Both 1 and 2.

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