Worker A takes 8 hours to do a job. Worker B takes 10 hour to do the same job. How long should it take both A and B, working together but independently, to do the same job?

Worker A takes 8 hours to do a job. Worker B takes 10 hour to do the same job. How long should it take both A and B, working together but independently, to do the same job?

A 4(4/9) days

B 4(4/7) days

C 4(3/8) days

D None of these

Solution

Correct Answer: Option A

working together, they can do 1/10+1/8=9/40

they can do the whole job in: 40/9 days=4(4/9) days