Approximate (nearest sensible option): 36.98276421 × 21.00002 = ?

Difficulty: Easy

Correct Answer: 775

Explanation:

Introduction: Products with one factor near an integer multiple lend themselves to quick rounding. Because 36.98… is close to 37 and 21.00002 is essentially 21, the result should be near 37 × 21, with negligible adjustment from tiny decimals.

Given Data / Assumptions:

  • First factor ≈ 37
  • Second factor ≈ 21
  • Options are spaced by 10 or more, so coarse rounding suffices.

Concept / Approach: Compute 37 × 21 = 777. Adjust slightly downward because the first factor is a bit below 37 (36.98…) while the second is a hair above 21. The net effect keeps the product near 777, closer to 775 than 785.

Step-by-Step Solution:

37 × 21 = 777 Refined product ≈ 36.9828 × 21.00002 ≈ 776.6–776.7 Closest option = 775

Verification / Alternative check: Exact multiplication (calculator) would yield about 776.64, which is 1.64 away from 775 and 8.36 from 785. Hence 775 is nearest.

Why Other Options Are Wrong: 785, 800, and 805 are too large; 770 is slightly farther than 775 from the refined estimate.

Common Pitfalls: Over-correcting for the tiny 0.00002 in the second factor; its impact is orders of magnitude smaller than the integer parts.

Final Answer: 775

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