Efficiency & Alterate Days Problem (2)

Duration: 6 min

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This video is a tutorial on solving a work and time problem involving the earnings of men and boys. The instructor, Yash Jain Sir, presents a question where the earnings of 5 men and 7 boys in 6 days and 2 men and 3 boys in 4 days are given, and the task is to find the time for 7 men and 6 boys to earn Rs. 750. The solution method involves setting up equations for the daily earnings of a man (M) and a boy (B), using the given data to find the individual daily earnings, and then calculating the total time required. The video uses a step-by-step approach, first finding the daily earning of a man and a boy, and then applying these values to the final scenario.

Chapters

  1. 0:00 – 2:00 00:00-02:00

    The video opens with a title card for a 'TIME & WORK' lesson, followed by a screen showing a multiple-choice question (Q1) about the earnings of men and boys. The instructor, Yash Jain Sir, introduces the problem: 'If 5 men with 7 boys can earn Rs. 127.50 in 6 days and 2 men with 3 boys can earn Rs. 35 in 4 days, then find the time in which 7 men with 6 boys will earn Rs. 750.' The options are (A) 20 days, (B) 25 days, (C) 15 days, (D) 30 days. The instructor begins to solve the problem by setting up the first equation: 5M + 7B = 127.50 in 6 days, which simplifies to 5M + 7B = 21.25 per day.

  2. 2:00 – 5:00 02:00-05:00

    The instructor continues to solve the problem by setting up the second equation from the given data: 2M + 3B = 35 in 4 days, which simplifies to 2M + 3B = 8.75 per day. He then uses the method of elimination to solve for the individual daily earnings. He multiplies the first equation (5M + 7B = 21.25) by 2 to get 10M + 14B = 42.5, and the second equation (2M + 3B = 8.75) by 5 to get 10M + 15B = 43.75. By subtracting the first new equation from the second, he finds that B = 1.25. Substituting this value back, he finds M = 2.5. The instructor then calculates the daily earning of 7 men and 6 boys as 7(2.5) + 6(1.25) = 17.5 + 7.5 = 25.

  3. 5:00 – 6:23 05:00-06:23

    With the daily earning of 7 men and 6 boys established as Rs. 25, the instructor calculates the time required to earn Rs. 750. He sets up the equation: 25 * x = 750, where x is the number of days. Solving for x, he finds x = 750 / 25 = 30 days. The final answer is 30 days, which corresponds to option (D). The video concludes with a summary of the steps and a 'THANKS FOR WATCHING' screen.

The video presents a clear, step-by-step solution to a classic work and time problem. It demonstrates the method of setting up a system of linear equations based on given work rates and then solving for the unknown individual rates. The core concept is that the total work (earnings) is the product of the rate (daily earning) and the time. By first determining the individual daily earnings of a man and a boy, the solution can be extended to any combination of workers. The method of elimination is used effectively to solve the system of equations, and the final answer is derived by simple division of the total amount by the combined daily rate.