Difficulty: Easy

Average Score: 78%

A student calculates the sum of 4.5 and .923 to be .968. Based on the student’s answer, which of the following best explains the student’s error?

Rationale

Incorrectly placing the decimal in the answer.

The student’s calculated sum of 4.5 and 0.923 should be 5.423, but the answer of 0.968 indicates a decimal placement error, suggesting that the student may have misaligned the decimal points during their calculation.

A (Incorrectly placing the decimal in the answer) CORRECT

This choice accurately identifies the student's mistake, as the misplacement of the decimal led to a significantly lower sum. Instead of arriving at 5.423, the student seems to have positioned the decimal point before the whole number, resulting in an incorrect and much smaller answer.

B (Subtracting the numbers instead of adding) YOUR ANSWER

If the student had subtracted instead of adding, the answer would not be 0.968. The subtraction of 4.5 from 0.923 would yield a negative number, which is not the case here. Therefore, this option does not explain the student's specific error.

C (Adding digits that do not represent the same place value) YOUR ANSWER

While it is essential to align digits by place value when adding, the student actually added them correctly in terms of place value but likely mismanaged the decimal point. This choice does not accurately reflect the nature of the student's error.

D (Making a regrouping error while adding) YOUR ANSWER

A regrouping error would suggest that the student failed to carry over values correctly, which is irrelevant in this case since the addition of 4.5 and 0.923 does not require regrouping. The student’s primary error stems from decimal placement, making this option incorrect.

Conclusion

The student's miscalculation of the sum of 4.5 and 0.923 to be 0.968 can be attributed to an incorrect placement of the decimal point. This key error resulted in a response that was not only numerically incorrect but also significantly lower than the actual sum of 5.423. Understanding the importance of decimal alignment is crucial in ensuring accuracy in arithmetic operations.

Related Questions

View all