Question

Three workers have to do a certain job. The first worker can finish the job in 8 hours. The second worker can finish the job in 4 hours. The third worker can also finish the job in 4 hours. How long will it take the three workers to finish the job if they work together?

Answer 1

since 2 and 3rd worker are double as fast at 1, they each take a part of work in a 1:2:2 proportion, which divides up the job into 5 parts, meaning each person will finish their part in 1.6 hours.