Approximation and quick calculation: Evaluate 6.39 × 128.948 + (5.215 ÷ 12.189) + 25.056 and select the closest option.

Difficulty: Easy

Correct Answer: 850

Explanation:


Introduction / Context:
The expression is dominated by the product 6.39*128.948. The division term is small (≈0.43), and the constant is modest. A careful product estimate plus the small add-ons will point clearly to the nearest option.


Given Data / Assumptions:

  • Main term: 6.39 * 128.948
  • Small term: 5.215 / 12.189
  • Constant: 25.056


Concept / Approach:
Approximate 128.948 ≈ 129; 6.39*129 = 6.39*(130 − 1) = 830.7 − 6.39 = 824.31. Add the small division (~0.43) and the constant 25.056 to reach the final estimate near 850.


Step-by-Step Solution:

6.39 * 128.948 ≈ 824.0–824.3 (tight range) 5.215 / 12.189 ≈ 0.43 Add constant 25.056 Total ≈ 824.2 + 0.43 + 25.056 ≈ 849.69 Nearest option: 850


Verification / Alternative check:
Exact computation gives about 849.46, still nearest to 850 compared with 800, 900, or 950.


Why Other Options Are Wrong:
800 is too low by ~49; 900 and 950 are too high. 850 is closest.


Common Pitfalls:
Ignoring the constant 25.056 or over-rounding 128.948 to 130 without subtracting the 6.39 correction.


Final Answer:
850

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