NECO 2005 Mathematics · Question 35

Evaluate log 18 + log6 - log1612^{\frac{1}{2}}

Options

  1. A.log 3
  2. B.log 9
  3. C.log 20
  4. D.3 log 2
  5. E.3 log 3

Answer: E. 3 log 3

Explanation written with AI and checked against the answer key

Analyze the question: We need to combine logs using the laws of logarithms. The expression is log 18 + log 6 − log 16^(1/2).

Concept:

  • log a + log b = log(ab)
  • log a − log b = log(a/b)
  • 16^(1/2) = √16 = 4

Solution:

Step 1: Simplify 16^(1/2) = 4.

Step 2: Rewrite the expression: log 18 + log 6 − log 4

Step 3: Combine: log (18 × 6 / 4) = log (108 / 4) = log 27

Step 4: Express 27 as a power of 3: log 27 = log 3³ = 3 log 3

Answer: 3 log 3, which is option E.

Tip: When you see a log problem, turn every sum into a product and every difference into a quotient, then look for perfect powers (like 27 = 3³, 8 = 2³) to match the options. Also, remember that a fractional power like 16^(1/2) is just a square root.

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