Discussion
A can do a piece of work in 7 days of 9 hours each day and B can do it in 6 days of 7 hours each day. then how many days they will take to do it, working together 8 hours a day:
Answer: C
Working together 8 hours a day, they need about 3 days.
Convert each worker's time to hours: A needs \(7 \times 9 = 63\) hours and B needs \(6 \times 7 = 42\) hours.
\[ \begin{aligned} \text{per hour} &= \frac{1}{63} + \frac{1}{42} = \frac{5}{126} \\ \text{hours} &= \frac{126}{5} = 25.2 \\ \text{days} &= \frac{25.2}{8} = 3.15 \end{aligned} \]
The exact figure is 3.15 days of 8 hours, which the options round to 3 days. 2 days (16 hours) is too short, since together they need more than 25 hours. 5 and 6 days are too long: B alone needs 42 hours, about 5.25 days of 8 hours, and adding A can only shorten that.
Post your comment
Please log in or register to post a comment.
Examination Categories
- SSC Exams
- Banking Exams
- Teaching Exams
- Civil Services Exams
- Railways Exams
- Engineering Recruitment Exams
- Defence Exams
- State Government Exams
- Police Exams
- Insurance Exams
- Nursing Exams
- Other Government Exams
- NRA CET
- PG Entrance Exams
- Campus Placement
- MBA Entrance Exams
- CUET and UG Entrance
- Judiciary Exams
- Regulatory Body Exams
- Software Development