Machine A can complete a target in 10 days. Machine B can complete the same in 20 days. Within how many days both machines complete target together?

Machine A’s time =1 target/10 days

Machine B’s time =1target /20 days

Both together =1/x days 

Solve for x. 

1/10 +1/20 =1/x 

3/20=1/x 

x =20/3

Both Machines will complete the target in6 days  8 hours

exect20/3 days

6.66 Days  i.e  7  Days  (Machine A6.66% of the task and Machine B3.33% of the task)