Difficulty: Easy
Correct Answer: 0.4471
Explanation:
Introduction / Context:We evaluate a common logarithm by breaking 2.8 into factors whose logs are known and using standard log identities.
Given Data / Assumptions:
Concept / Approach:Write 2.8 = 28/10 = (4×7)/10, then apply log(A/B) = log A − log B and log(AB) = log A + log B.
Step-by-Step Solution:
log(2.8) = log(28) − log(10)log(28) = log(4×7) = log 4 + log 7 = 2·log 2 + log 7Compute: 2·0.3010 + 0.8451 = 0.6020 + 0.8451 = 1.4471Subtract log 10 = 1: 1.4471 − 1 = 0.4471Verification / Alternative check:2.8 ≈ 10^0.4471 (since 10^0.4471 ≈ 2.8), confirming consistency with the computed value.
Why Other Options Are Wrong:1.4471 is log 28; 2.4471 or 14.471 are orders of magnitude too large; 0.4471 is the only value matching log 2.8.
Common Pitfalls:Forgetting to subtract 1 when converting from log 28 to log 2.8 (since 2.8 = 28/10) yields the common mistake 1.4471 instead of 0.4471.
Final Answer:0.4471
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