Evaluate the expression (0.96)^3 − (0.1)^3 divided by [ (0.96)^2 + (0.96*0.1) + (0.1)^2 ]. Use the a^3 − b^3 factorization to simplify.

Difficulty: Easy

Correct Answer: 0.86

Explanation:


Introduction / Context:
This expression is designed for the identity a^3 − b^3 = (a − b)(a^2 + ab + b^2). When the denominator matches a^2 + ab + b^2, the overall fraction collapses to a − b. Recognizing such structures converts a potentially tedious decimal computation into a one-step result.


Given Data / Assumptions:

  • a = 0.96, b = 0.10.
  • Expression: [a^3 − b^3] / [a^2 + ab + b^2].
  • Note that ab = 0.96 * 0.10 = 0.096 (as written).


Concept / Approach:
Apply the cube difference factorization. Since the denominator equals a^2 + ab + b^2 exactly, the expression simplifies to a − b immediately. Then compute 0.96 − 0.10 to reach the final answer without rounding issues.


Step-by-Step Solution:
Use identity: a^3 − b^3 = (a − b)(a^2 + ab + b^2).Given denominator = a^2 + ab + b^2, the ratio = a − b.Compute a − b = 0.96 − 0.10 = 0.86.


Verification / Alternative check:
Approximate directly: (0.884736 − 0.001) / (0.9216 + 0.096 + 0.01) ≈ 0.883736 / 1.0276 ≈ 0.86 (rounded), confirming the identity-based result.


Why Other Options Are Wrong:

  • 1.06 / 0.95 / 0.97 / 0.80: These values arise from arithmetic slips or from misreading the denominator as a^2 + a + b^2 or using 0.96 instead of 0.096 for ab.


Common Pitfalls:
Misreading 0.096 as 0.96; attempting to compute the cubes fully and rounding at intermediate steps; forgetting the identity and overcomplicating the work.


Final Answer:
0.86

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