Type 6.3 Important Practice Questions

Duration: 11 min

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This educational video is a lecture on coding-decoding problems, a common topic in competitive exams. The instructor, Yash Jain, begins by introducing the concept of a coding system where each letter is assigned a number. He demonstrates a specific example where the word 'MONKEY' is coded as 'KMLICW', and the word 'ORANGE' is to be decoded. The solution is derived by identifying a pattern: each letter in the original word is shifted backward by two positions in the alphabet (a ROT13 cipher). The video then transitions to a series of practice questions. The first question shows 'ACID' coded as '1C3D', which is a substitution cipher where the letter 'C' is replaced by the number '3'. The second question shows 'ACID' coded as '1233', which is a positional cipher where each letter is replaced by its position in the alphabet (A=1, C=3, I=9, D=4). The instructor systematically works through these problems, explaining the logic and method for each type of coding-decoding puzzle. The video concludes with a final 'THANKS FOR WATCHING' screen.

Chapters

  1. 0:00 – 2:00 00:00-02:00

    The video opens with a title slide titled 'CODING DECODING'. It presents a problem: 'MONKEY' is coded as 'KMLICW', and the task is to decode 'ORANGE'. The instructor explains the pattern by showing the alphabetical positions of the letters in 'MONKEY' (13, 15, 14, 11, 5, 25) and the corresponding coded numbers (11, 13, 9, 3, 3, 23). He identifies that each number is reduced by 2, which corresponds to shifting each letter back by two positions in the alphabet. The slide concludes with the statement, 'So, each alphabet of ORANGE should be decreased by 2 alphabet', setting up the solution for the problem.

  2. 2:00 – 5:00 02:00-05:00

    The video transitions to a new section titled 'Questions Type 6'. The instructor presents three different coding problems. The first is 'ACID = 1C3D', the second is 'ACID = 1233', and the third is 'ACID = 1233' with 'BOMBAY = B4MB1Y'. The instructor begins to analyze the first problem, 'ACID = 1C3D', by writing the alphabet and assigning numbers to each letter (A=1, B=2, C=3, etc.). He explains that this is a substitution cipher where the letter 'C' is replaced by the number '3'. He then moves to the second problem, 'ACID = 1233', and explains that this is a positional cipher where each letter is replaced by its position in the alphabet (A=1, C=3, I=9, D=4). He notes that the code '1233' is incorrect for 'ACID' and that the correct code should be '1394'.

  3. 5:00 – 10:00 05:00-10:00

    The instructor continues to work through the coding problems. He analyzes the third problem, 'ACID = 1233' and 'BOMBAY = 141112', and identifies that the code is based on the position of the letters in the alphabet. He then moves to the problem 'ACID = 9' and 'BOMBAY = 37', which is a different type of problem where the sum of the positions of the letters is calculated. He explains that for 'ACID', the sum is 1+3+9+4=17, but the code is 9, so he must be missing something. He then analyzes the problem 'ACID = 1C3D' and 'BOMBAY = B4MB1Y', which is a substitution cipher where the letter 'C' is replaced by '3' and 'B' is replaced by '4'. He then moves to the problem 'ACID = 1233' and 'BOMBAY = 14101120', which is a positional cipher where each letter is replaced by its position in the alphabet. He explains that the code '14101120' is incorrect for 'BOMBAY' and that the correct code should be '214121525'. He then moves to the problem 'ACID = 1233' and 'BOMBAY = 141112', which is a positional cipher where each letter is replaced by its position in the alphabet. He explains that the code '141112' is incorrect for 'BOMBAY' and that the correct code should be '214121525'. He then moves to the problem 'ACID = 9' and 'BOMBAY = 37', which is a different type of problem where the sum of the positions of the letters is calculated. He explains that for 'ACID', the sum is 1+3+9+4=17, but the code is 9, so he must be missing something.

  4. 10:00 – 10:38 10:00-10:38

    The video concludes with a final screen that displays the text 'THANKS FOR WATCHING' in large white letters against a dark red background. This is a standard closing slide for the educational content, indicating the end of the lecture.

The video provides a comprehensive tutorial on solving coding-decoding problems, a key skill for competitive exams. It begins with a clear, step-by-step demonstration of a letter-shifting cipher (ROT13), using the example of 'MONKEY' to 'KMLICW' to establish the core concept. The instructor then systematically introduces and explains different types of coding systems, including substitution ciphers (where letters are replaced by numbers, e.g., 'C' becomes '3') and positional ciphers (where letters are replaced by their alphabetical position, e.g., 'A' becomes '1'). The progression from a simple example to a series of practice questions allows students to apply the learned methods. The video effectively uses on-screen text and handwritten annotations to illustrate the logic, making it a valuable resource for understanding the fundamental patterns in this type of logical reasoning problem.