If log<sub>10</sub>7 = a, evaluate log<sub>10</sub>(1/70).
Aptitude
Logarithm
Difficulty: Easy
Choose an option
-
A1 - a
-
Ba - 1
-
C-a - 1
-
D-a + 1
Answer
Correct Answer: -a - 1
Explanation
Concept / Approach
- Use product/quotient rules and the facts: log1010 = 1 and log101 = 0.
Step-by-step calculationlog10(1/70) = log101 - log1070= 0 - [log107 + log1010]= 0 - [a + 1] = -a - 1
Common pitfalls
- Forgetting to include the +1 from log1010.
Final Answer-a - 1