NECO 2005 Mathematics · Question 35
Evaluate log 18 + log6 - log16
Options
- A.log 3
- B.log 9
- C.log 20
- D.3 log 2
- 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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