Final answer:
Darko most likely made the error of multiplying the numbers instead of adding them. The addition of 324 and 57 correctly results in 381, not 894. The multiplication of these numbers does yield a product in the vicinity of 894, suggesting this is where Darko's calculation may have gone awry.
Step-by-step explanation:
The student, Darko, found the sum of 324 and 57 to be 894. To identify the error Darko made, we should first calculate the correct sum of these two numbers. When we add 324 and 57, aligning the digits by their place values, we get:
324
+57
----
381
The correct sum is 381, not 894. So, looking at the options provided:
A. Darko added 324 and 75 by mistake. (This would yield 399, not 894.)
B. Darko did not align the digits by their place value when he set up the problem. (There’s no clear evidence of this from the result.)
C. Darko did not regroup correctly after adding the ones digits. (The incorrect total does not suggest a regrouping error.)
D. Darko multiplied the numbers instead of adding them. (Multiplying 324 by 57 indeed gives a product close to 894, specifically 18468, if we misplace the decimal or forget to place a digit, we might incorrectly report a product of 894.)
Therefore, the most likely error Darko made is D. Darko multiplied the numbers instead of adding them.