Find the units digit of the sum 4198 + 612345 + 34866 + 2411 + 1.

Introduction / Context:
This problem asks for the units digit of a sum of several numbers. Instead of adding the full numbers, we can use the idea that only the units digits affect the units digit of the final sum. This is a common time saving trick in aptitude tests when dealing with large numbers or long sums.

Given Data / Assumptions:

- The numbers are 4198, 612345, 34866, 2411 and 1. - We want only the units digit of the total sum. - Basic properties of addition and place value apply.

Concept / Approach:
The units digit of a sum depends only on the units digits of the addends. Higher place digits contribute to carries but do not change the final units digit beyond that carry. Therefore, we can ignore all except the units digits, add those, and then extract the units digit of that result. This is much faster than performing full long addition.

Step-by-Step Solution:
Step 1: Identify the units digit of each number. Step 2: For 4198, the units digit is 8. Step 3: For 612345, the units digit is 5. Step 4: For 34866, the units digit is 6. Step 5: For 2411, the units digit is 1. Step 6: For 1, the units digit is 1. Step 7: Add these units digits: 8 + 5 + 6 + 1 + 1. Step 8: Compute the sum: 8 + 5 = 13, 13 + 6 = 19, 19 + 1 = 20, 20 + 1 = 21. Step 9: The units digit of 21 is 1.

Verification / Alternative check:
If desired, we can add the full numbers or check with partial sums. Adding 4198 and 612345 gives 616543, then adding 34866 gives 651409, adding 2411 gives 653820 and finally adding 1 gives 653821. The units digit of 653821 is 1, which confirms our shortcut method. However, using only units digits is clearly much faster and less error prone.

Why Other Options Are Wrong:
Options A (3), B (2) and D (0) correspond to incorrect totals of the units digits or to arithmetic mistakes in handling carries. Since the exact sum ends in 1, none of these options can be correct.

Common Pitfalls:
Errors often occur from misreading one of the numbers or misadding the units digits. Another trap is to think that tens digits or higher are needed, which leads to unnecessary work and increases the chance of mistakes. Focusing only on the units digits and working carefully with the small sum is the best strategy.

Final Answer:
The units digit of the sum 4198 + 612345 + 34866 + 2411 + 1 is 1, which corresponds to option C.