Aptitude Problems on Logarithm – Tips and Tricks to Solve in IBPS PO and Clerk Exams with Examples
Hello students, I am Rahul Sir from OdTutor, and over the years of training aspirants for IBPS PO, IBPS Clerk, SBI PO, SBI Clerk, SSC, and Railway examinations, I have seen one topic consistently intimidate students who are otherwise quite well-prepared — Logarithm. The moment students see the word “log” in a question, something switches off in their brain. They skip it, mark it for later, and often never return to it during the exam, losing easy marks in the process. Here is the truth I tell every batch of students I teach: Logarithm is one of the most formula-friendly chapters in the entire quantitative aptitude syllabus. It does not require lengthy calculations, it does not require complex reasoning, and once you understand what a logarithm actually means, the formulas feel logical rather than arbitrary. You stop memorizing and start understanding, and that makes all the difference. At OdTutor, I have developed a step-by-step teaching approach for Logarithm that takes even the most hesitant student from absolute confusion to confident problem-solving within a matter of days. In this article, I am going to walk you through every important concept, formula, and question type that IBPS PO and Clerk exams test, with clear solved examples at every stage. Read it from beginning to end, practice the examples alongside, and I promise you — Logarithm will become one of your favorite scoring topics in the exam. Let’s get started. 1. What Exactly Is a Logarithm? The Concept Explained Simply Before any formula, any shortcut, or any trick, you must understand what the word “logarithm” actually means. I spend a full 20 minutes on this in my live classes, because every single formula that comes afterward is rooted in this one definition. Consider this simple question: “To what power must we raise 2 to get 8?” You already know the answer — 2 raised to the power 3 gives 8, so the answer is 3. Logarithm is simply a way of writing this question and its answer in a formal mathematical notation. We write it as: log₂(8) = 3 This is read as “log base 2 of 8 equals 3,” and it means exactly the same thing as 2³ = 8. The general definition is: logₐ(b) = c means aᶜ = b Here, ‘a’ is called the base, ‘b’ is the number whose logarithm is being taken, and ‘c’ is the answer — the exponent to which ‘a’ must be raised to get ‘b’. I give my students this mental anchor: the logarithm answers the question “what is the exponent?” That’s all it is. Every time you see logₐ(b), your brain should immediately ask: “a raised to WHAT power gives b?” The answer to that question is your logarithm value. This conversion between logarithmic form and exponential form is the very first skill you must master, because every property and formula of logarithm is simply the exponential rule rewritten in log language. Get this conversion absolutely smooth, and the rest of the chapter flows naturally. 2. Essential Properties of Logarithm You Must Know by Heart Now that the definition is clear, let’s build the formula toolkit. These properties appear directly or indirectly in almost every Logarithm question in IBPS exams. I want you to not just memorize them, but understand why each one makes sense based on what you already know about exponents. Property 1 — Product Rule: log(m × n) = log m + log n When you multiply two numbers, their logs add. This mirrors the exponent rule: aˣ × aʸ = aˣ⁺ʸ. Property 2 — Quotient Rule: log(m / n) = log m − log n When you divide two numbers, their logs subtract. This mirrors: aˣ / aʸ = aˣ⁻ʸ. Property 3 — Power Rule: log(mⁿ) = n × log m An exponent inside a log comes out as a multiplier in front. This is extremely frequently tested. Property 4 — Change of Base Rule: logₐ(b) = log(b) / log(a) This lets you convert any log to base 10, which makes calculations far easier. Property 5 — Log of 1: logₐ(1) = 0 for any base a Because a⁰ = 1 always, the log of 1 is always 0 regardless of the base. Property 6 — Log of Base Itself: logₐ(a) = 1 Because a¹ = a always, the log of the base equals 1. Property 7 — Log Base Reciprocal: logₐ(b) = 1 / logᵦ(a) Switching the base and the number gives you the reciprocal. This is a lifesaver in competitive exams. Write all seven properties on a single sheet. Review them every morning for one week until you can write all seven from memory in under two minutes. 3. Solved Examples: Applying Basic Properties Let’s immediately put those properties to work with examples that mirror the style of actual IBPS questions. Example 1: Find the value of log₂(32). Solution: We need to find: 2 raised to what power gives 32? Since 32 = 2⁵, we have log₂(32) = 5. That’s it. Example 2: Simplify: log(6) + log(5) − log(3) Solution: Using Product Rule first: log(6) + log(5) = log(6 × 5) = log(30) Then using Quotient Rule: log(30) − log(3) = log(30/3) = log(10) = 1 (Since log base 10 of 10 = 1, and when no base is written, base 10 is assumed.) The answer is 1. Example 3: Simplify: log₃(81) − log₃(9) Solution: log₃(81) = log₃(3⁴) = 4 log₃(9) = log₃(3²) = 2 Answer = 4 − 2 = 2 Alternatively using Quotient Rule: log₃(81/9) = log₃(9) = 2. Same answer. Example 4: If log(2) = 0.3010, find log(8). Solution: log(8) = log(2³) = 3 × log(2) = 3 × 0.3010 = 0.9030 This is a hugely important question type. IBPS almost always gives you a standard log value and asks you to calculate another one by expressing it as a power of a given number. I will cover this pattern extensively in the coming sections. 4. The Standard Log Values You Must Memorize








