Difficulty: Medium
Correct Answer: 20
Explanation:
Introduction / Context:
The expression equates a product of powers on the left to 2 times a square on the right. Solving for the base of the square requires isolating (?)^2 and taking a square root. Because the bases are near 10 and 2, the left-hand product is near 10^2 × 2^3 = 800, making the square root arithmetic tidy.
Given Data / Assumptions:
Concept / Approach:
First compute the left-hand side approximately. Then set 2 * (?)^2 ≈ LHS, so (?) ≈ sqrt(LHS/2). Compare the result to the available integer options and select the nearest match.
Step-by-Step Solution:
Verification / Alternative check:
Using tighter arithmetic gives ? ≈ 20.05. Among the options, 20 is the closest integer and balances both sides very well within the intended approximation level.
Why Other Options Are Wrong:
Common Pitfalls:
Taking square root before dividing by 2, or attempting to over-round bases (e.g., 9.95→9) which can skew the final square root noticeably.
Final Answer:
20
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