Set 6- Important Questions on Logarithms

Duration: 11 min

This video lesson is available to enrolled students.

Return to /learn/APTITUDE-FOR-PLACEMENT/aptitude/logarithm/solving-logarithmic-expressions-and-equations/asset-set-6-important-questions-on-logarithms after enrolling

Inside: a video lesson and guided study material.

Module outline

  1. Aptitude: Ratio and Proportion (Ratios), Divisibility Rules, Data Interpretation, Mixture and Alligation, Permutation and Combination, Logarithm, Number System, HCF LCM, Sequence and Series (Series), Speed Time and Distance, Percentage, Average, Powers and Exponents (Surds and Indices), Algebra, Probability, Profit and Loss, Simple Interest and Compound Interest, Time and Work, Pipe and Cistern, TCS NQT Advanced Quantitative Ability, Speed Mathematics and Basic Mathematics, Arithmetic, Statistics, Partnership, Age Problems, Mental Ability, Mensuration and Geometry, Linear Algebra, Calculus, Trigonometry, Vectors, Gamified / Game Based Aptitude
  2. Reasoning: Series (Number and Letter Series) (Numerical Relations and Reasoning), Coding Decoding, Data Sufficiency, Non Verbal Reasoning (Spatial Aptitude) (Spatial Reasoning) (Visual Reasoning), Deductive and Inductive Reasoning (Logical Deduction and Induction) (Prepositional Reasoning), Syllogisms, TCS NQT Advanced Reasoning Ability, Ranking, Order and Sequence, Analogy, Inequality, Data Arrangement, Venn Diagram, Logical Sequence Of Words, Selection Decision Table (Decision Making), Cubes & Dices, Clock, Calendar, Puzzle Solving (Puzzles), Analytical Reasoning (Counting Figures Reasoning), Directions (Direction Test), Blood Relations, Seating Arrangements
  3. Verbal Ability (English): Vocabulary, Noun, Subject Verb Agreement (Verb Noun Agreement), Adjectives, Tenses, Pronoun, Preposition, Articles, Direct and Indirect Speech, Conjunction, Modals, Sentence Re-arrangements (Para Jumbles) (Narrative Sequencing), Sentence Correction (Error Correction), Sentence Completion (Fill in the blanks), Comprehension / Reading Comprehension / Unseen Passages (Critical Reasoning) (Paragraph Questions), Cloze Test (Cloze Passage), Verbal Analogy (Word Based Analogy), Sentence Construction, Active Passive Voice (Voice), Determiner, Facts, Inference and Judgements, Adverb, Verb
  4. Mega Test:
  5. Grand Test:
AI summary & chapters

AI Summary

An AI-generated summary of this video lecture.

This educational video is a lecture on logarithms, presented by Yash Jain from Knowledge Gate Eduventures. The video begins with an introduction to the topic, followed by a series of practice problems. The first problem asks for the value of a + b + c given that log a + log b + log c = 0 for non-negative integers a, b, and c. The instructor applies the logarithmic property log m + log n = log(mn) to simplify the equation to log(abc) = 0, which implies abc = 1. Since a, b, and c are non-negative integers, the only solution is a = b = c = 1, leading to a + b + c = 3. The second problem is similar but for integers a, b, and c, with the condition log |a| + log |b| + log |c| = 0. This simplifies to |a||b||c| = 1, meaning the product of their absolute values is 1. The instructor then finds the minimum and maximum possible values of a + b + c by considering the combinations of positive and negative integers whose absolute values multiply to 1. The final problem involves solving for y given log_y(5/7) = -1/3, which is solved by converting the logarithmic equation to its exponential form, y^(-1/3) = 5/7, and then finding y = (7/5)^3 = 343/125. The video concludes with a 'Thanks for watching' screen.

Chapters

  1. 0:00 – 2:00 00:00-02:00

    The video opens with a title card for a lecture on logarithms by Yash Jain. The main content begins with a problem statement on a yellow background: 'Que: (Set6) For non-negative integers a, b and c, what would be the value of a + b + c if log a + log b + log c = 0.' The instructor, visible in a small window, begins to solve the problem. He first applies the logarithmic property log m + log n = log(mn) to the given equation, writing 'log(abc) = 0' on the screen. He then explains that this implies abc = 1, as log_x(1) = 0 for any base x. He notes that a, b, and c are non-negative integers, so the only way for their product to be 1 is if all three are 1. He writes 'a=1, b=1, c=1' and calculates the sum as 3.

  2. 2:00 – 5:00 02:00-05:00

    The instructor transitions to the next problem: 'Que: (Set6) For integers a, b and c, what would be the minimum & maximum value respectively of a + b + c if log |a| + log |b| + log |c| = 0.' He explains that the absolute values are used because the logarithm of a negative number is not defined in the real number system. He applies the same logarithmic property to get log(|a||b||c|) = 0, which means |a||b||c| = 1. He then considers the possible integer values for a, b, and c. Since the product of their absolute values is 1, each of |a|, |b|, and |c| must be 1. Therefore, a, b, and c can each be either 1 or -1. To find the minimum sum, he considers the case where all three are -1, giving a sum of -3. To find the maximum sum, he considers the case where all three are 1, giving a sum of 3. He writes 'min = -3' and 'max = 3' on the screen.

  3. 5:00 – 10:00 05:00-10:00

    The video presents the final problem: 'Que: (Set6) log_y(5/7) = -1/3, find y?'. The instructor begins by explaining that to solve for the base y, he needs to convert the logarithmic equation into its exponential form. He writes the conversion rule: 'log_b(a) = c' is equivalent to 'b^c = a'. Applying this to the problem, he writes 'y^(-1/3) = 5/7'. To solve for y, he takes the reciprocal of both sides, which gives 'y^(1/3) = 7/5'. He then cubes both sides to get 'y = (7/5)^3'. He calculates this as '343/125'. He also notes that the base y must be positive and not equal to 1, which is satisfied by the solution.

  4. 10:00 – 10:34 10:00-10:34

    The video concludes with a black screen displaying the text 'THANKS FOR WATCHING' in white and orange. The text is centered on the screen, with 'THANKS' in a large orange box and 'FOR WATCHING' below it in white. A thin orange line is drawn underneath the text. This is a standard closing screen for the educational video.

The video presents a structured lesson on logarithms, progressing from basic properties to more complex problem-solving. It begins with a problem that reinforces the product rule of logarithms and the definition of a logarithm, leading to a simple integer solution. The second problem introduces the concept of absolute values to handle negative numbers, demonstrating how to find the range of a sum under a logarithmic constraint. The final problem applies the fundamental conversion between logarithmic and exponential forms. The progression shows a clear pedagogical flow, moving from foundational concepts to their application in solving for unknowns, which is typical for a mathematics tutorial.

Loading lesson…