Evaluate a nested decimal expression accurately: 3 / [ 3 + {(0.3 − 3.03) / (3 × 0.91)} ] = ?
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A1.5
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B15
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C0.75
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D1.75
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E1.25
Answer
Correct Answer: 1.5
Explanation
Introduction / Context:This question checks precision with signed decimals and order of operations inside a complex denominator. Spotting simple cancellation makes the computation almost trivial once the inner fraction is recognized.
Given Data / Assumptions:
- Expression: 3 / [ 3 + {(0.3 − 3.03) / (3 × 0.91)} ]
- All decimal arithmetic is exact; keep the sign when subtracting.
Concept / Approach:Simplify the inner fraction first by computing its numerator and denominator. If they share magnitude (up to sign), the fraction becomes −1. Then evaluate the outer denominator and finally perform the division.
Step-by-Step Solution:Inner numerator: 0.3 − 3.03 = −2.73.Inner denominator: 3 × 0.91 = 2.73.Thus inner fraction = −2.73 / 2.73 = −1.Overall denominator: 3 + (−1) = 2.Final value: 3 / 2 = 1.5.
Verification / Alternative check:Convert to fractions out of 100 (e.g., 0.91 = 91/100) and observe exact cancellation to confirm the −1 step rigorously.
Why Other Options Are Wrong:
- 15: As if multiplying instead of dividing by 2.
- 0.75: Inverts the final fraction 3/2 improperly.
- 1.75 and 1.25: Arise from arithmetic slips in the denominator (e.g., adding signs incorrectly).
Common Pitfalls:Losing the negative sign from 0.3 − 3.03; miscomputing 3 × 0.91 as 2.79; or forgetting to simplify the inner term before the outer operations.
Final Answer:1.5