Given log10 57 ≈ 1.756 and log10 0.57 = log10(57) − 2 ≈ −0.244, evaluate: log 57 + log(0.57)^3 + log √(0.57).

Difficulty: Medium

Correct Answer: 0.902

Explanation:


Introduction / Context:
We combine logs using properties: log(a^k) = k log a and log a + log b = log(ab). The expression contains powers of the same positive number (0.57), which we merge systematically.


Given Data / Assumptions:

  • log10 57 ≈ 1.756.
  • log10 0.57 = log10 57 − 2 ≈ −0.244.
  • Expression: log 57 + log(0.57)^3 + log √(0.57).


Concept / Approach:

  • Interpret log(0.57)^3 as log((0.57)^3) = 3 log(0.57).
  • Similarly, log √(0.57) = (1/2) log(0.57).


Step-by-Step Solution:

S = log 57 + 3 log 0.57 + (1/2) log 0.57= log 57 + 3.5 log 0.57≈ 1.756 + 3.5(−0.244) = 1.756 − 0.854 ≈ 0.902


Verification / Alternative check:
Combine inside a single log: S = log[57 * (0.57)^{3.5}] and evaluate numerically; the same value results to three decimals.


Why Other Options Are Wrong:

  • 1.902 and 2.146 add instead of subtracting the negative contributions.
  • 1.146 is from rounding incorrectly.


Common Pitfalls:

  • Misreading log(0.57)^3 as (log 0.57)^3; here the intended property is log(a^k).


Final Answer:
0.902

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