Compute the decimal product accurately: 8.32 × 0.999. Use the idea that 0.999 = 1 − 0.001 for a quick evaluation.

Difficulty: Easy

Correct Answer: 8.31168

Explanation:


Introduction / Context:
Multiplying by 0.999 can be done very quickly by using the identity 0.999 = 1 − 0.001. This method reduces multiplication to a simple subtraction, minimizing rounding errors and mental effort.


Given Data / Assumptions:

  • Value to compute: 8.32 × 0.999
  • All decimals are exact; do not round prematurely.


Concept / Approach:
Rewrite 0.999 as 1 − 0.001. Then 8.32 × 0.999 = 8.32 × (1 − 0.001) = 8.32 − 0.00832. Simple subtraction then yields the precise product.


Step-by-Step Solution:
0.999 = 1 − 0.001.8.32 × 0.999 = 8.32 − (8.32 × 0.001) = 8.32 − 0.00832.Result = 8.31168.


Verification / Alternative check:
Standard multiplication also gives 8.31168. You can cross-check by noting that the answer must be slightly less than 8.32 (by exactly 0.00832).


Why Other Options Are Wrong:

  • 8.31668 or 8.31618: Subtracting 0.00332 or 0.00382 instead of 0.00832.
  • 0.831168: Misplaced decimal point by one order of magnitude.
  • 8.32168: Incorrectly adding instead of subtracting the small adjustment.


Common Pitfalls:
Misplacing the decimal when computing 8.32 × 0.001; adding rather than subtracting; copying errors in digits.


Final Answer:
8.31168

Discussion & Comments

No comments yet. Be the first to comment!
Join Discussion