Question

Worker a takes 8 hours to do a job. Worker b takes 10 hours to do a job. How long should it take both a and b, working together to do same job.

Answer 1

Answer:

Step-by-step explanation:

A does in 8 hours. Hence, he does 1/8 part of job in 1 hour.

Similarly, B does 1/10 of job in 1 hour.

When they will work together on same job, they will do [(1/8)+(1/10)] of the job in one hour.

1/8+1/10⇒ (5+4)/40

              ⇒  9/40

They do 9/40 of job in 1 hour. 

So, they do the job in 40/9 days. {40/9 days= 4.4 days or 4 days and 6 hours)

Hope it helps you....

Answer 2

Answer

One hour work of:

A = 1/8

B = 1/10

1/A + 1/B = 1/8 + 1/10

= 18/80

= 9/40

A + B = 40/9 = 4.45 hours