Q18 Find the sum of the digits in the unit place of all 4 digit numbers formed using 3, 4, 5, and 6 without
any repetition.
1. 54
2. 90
3. 108
4. 219

Find the Sum of the Digits in the Unit Place of All 4-Digit Numbers Formed Using 3, 4, 5, and 6 Without Repetition

To solve this, let’s break down the problem step-by-step:

Step 1: Total Number of Possible 4-Digit Numbers

• We are given 4 digits: 3, 4, 5, 6
• All digits must be used without repetition.
• The total number of possible 4-digit numbers = 4!=24

Step 2: Contribution of Each Digit in the Unit Place

• Each digit (3, 4, 5, 6) will appear in the unit place an equal number of times.
• The number of times each digit will appear in the unit place:
• 24/4  = 6

Step 3: Sum of the Digits

Sum of all digits used = 3+4+5+6=18

Since each digit appears 6 times in the unit place, the total sum of the unit place digits is:

18×6=108

Final Answer:

The sum of the digits in the unit place of all 4-digit numbers is 108.

👉 Correct Answer: (3) 108