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JAMB Mathematics 1980 Question 38

Question 38

Logarithms

Given log 2 = 0.69, log 3 = 1.10 and log 7 = 1.90 all to a fixed base, find log 10.5 to the same base, without using tables.

  1. A.1.03
  2. B.2.31
  3. C.3.69
  4. D.10.5
  5. E.1.69.
Show the answer and explanation

Answer: B (2.31)

Explanation

10.5 = 3 × 7 ÷ 2, so log 10.5 = 1.10 + 1.90 − 0.69 = 2.31.